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Electrocardiographic computer |
| RE29921 |
Electrocardiographic computer
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| Patent Drawings: | |
| Inventor: |
Cherry, et al. |
| Date Issued: |
February 27, 1979 |
| Application: |
05/899,241 |
| Filed: |
April 24, 1978 |
| Inventors: |
Anderson; Donald L. (San Juan Capistrano, CA)
Cherry; Isaac R. (Mission Viejo, CA)
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| Assignee: |
Del Mar Avionics (Irvine, CA) |
| Primary Examiner: |
Nusbaum; Mark E. |
| Assistant Examiner: |
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| Attorney Or Agent: |
Smyth, Pavitt, Siegemund, Jones & Martella |
| U.S. Class: |
360/73.05; 360/90 |
| Field Of Search: |
364/2MSFile; 364/9MSFile; 128/2.6A; 128/2.6G; 128/2.6B; 128/2.6F; 128/2.6R; 346/33ME; 360/73; 360/73R; 360/90; 179/100.15 |
| International Class: |
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| U.S Patent Documents: |
T916007; 3728685; 3810102; 3815100; 3909792; 3913567; 3922686; 3934267; 4006737 |
| Foreign Patent Documents: |
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| Other References: |
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| Abstract: |
A multi-speed ECG magnetic tape scanning device for processing and observing in a relatively short interval of time large quantities of ECG signals from two pairs of ECG leads. The ECG information is recorded on a miniature recorder which the patient carries to record the information for a long period of time, such as 24 hours. The recorder includes a built-in clock with a visible display. The recorder also includes an event marker, which is activated by the patient when the patient experiences an event. The play-back of the ECG information is in real time or at multiple high speed play-back speeds of 30, 60 and 120 times real time. During play-back at high speed, a multi-speed multi-channel paper writer reproduces analog trend data, digital printed data and event marking. The trend information is usually heart rate and ST segment level, so as to produce a scanning of an entire 24 hour information tape in as short a period as 12 minutes. The tape scanning device can run on trend to print out trend to the end of the tape, and then stop automatically. Alternatively, the tape scanning device can run on trend to the end of the tape and then automatically cycle to the beginning of the tape to print-out trend and periodically slow the tape down to real time for the print-out of predetermined events in real time. After each print-out in real time, the playback always goes back to the originally selected trend speed for the continuation of the trend print-out. Various short events may be used to slow the read-out to real time, such as an event marking on the tape which has been activated by the patient. Also, any preselected abnormalities in heart function such as abnormal VE's, SVE's, ST level, rapid heart beat, slow heart rate, etc., may be used to print-out in real time. An arrhythmia computer detects and digitally displays the number of premature ventricular contractions (VE) and superventricular ectopic beats (SVE) and actuates the event markers on a paper writer when the arrhythmia occurrences exceed a predetermined number of occurrences during a predetermined time interval. The event marking may also be used to control the slow down during trend read-out to print out the ECG signals in real time to show the arrhythmia occurrences. The arrhythmia computer includes the ability to select one or a number of parameters to determine the occurrence of an arrhythmia. These parameters may be paired beats, prematurity, width or amplitude. |
| Claim: |
We claim:
1. A dynamic multispeed ECG computer for reproducing ECG information contained on a recording medium recorded at a particular speed, including:
first means for moving the recording medium past at least one fixed predetermined real time readout position and at least one fixed predetermined high speed readout position,
second means coupled to the first means for controlling the first means to move the recording medium at a selected one of a plurality of speeds including the particular speed and including more than one speed appreciably greater than theparticular speed, to provide real time and high speed playbacks respectively of the recorded information,
third means located at the fixed predetermined high speed readout position for reproducing the recorded information when the first means moves the recording medium to provide high speed playback,
fourth means located at the fixed predetermined real time readout position for reproducing the recorded information when the first means moves the recording medium to provide real time playback,
fifth means coupled to the third means and responsive to the reproduced signals at high speed playback for producing output signals in accordance with the trend of particular characteristics of the ECG complexes at high speed playback,
sixth means coupled to the third means and responsive to the reproduced signals for producing control signals indicative of the occurrence of the predetermined events within the characteristics of the ECG complexes, and
seventh means coupled to the sicth means and the second means and responsive to the control signals provided by the sixth means for controlling the second means to move the recording medium at the real time playback speed upon the occurrence ofthe predetermined events within the characteristics of the ECG complexes.
2. The ECG computer of claim 1 additinally including eighth means including a paper writer for reproducing the trend output signals and the paper writer operating at a speed to reproduce the trend output signals on a portion of the paper charthaving a length equal to small fraction of the length of recording medium, and for reproducing the ECG signals and the paper writer operating at a speed to reproduce the ECG signals on a portion of the paper chart on a real time basis.
3. The ECG computer of claim 2 wherein the fifth means produces trend output signals representing heart beat rate and ST level and wherein the paper writer provides a two channel writeout of the trend information on the trend chart.
4. The ECG computer of claim 2 additionally including ninth means for producing a digital printout of time related to the time of recording of the ECG signals on a real time basis.
5. The ECG computer of claim 1 wherein the sixth means is responsive to the ectopic beats in the ECG information reproduced at high speed playback for producing the control signals.
6. The ECG computer of claim 1 wherein the sixth means is responsive to VE ectopic beats in the ECG information for producing the control signals.
7. The ECG computer of claim 1 wherein the sixth means is responsive to SVE ectopic beats in the ECG information for producing the control signals.
8. The ECG computer of claim 1 wherein the sixth means is responsive to a number of ectopic beats in the ECG information exceeding a predetermined number in a predetermined unit time for producing the control signals.
9. The ECG computer of claim 1 wherein the sixth means is responsive to a number of VE ectopic beats in the ECG information exceeding a predetermined number in a predetermined unit time for producing the control signals.
10. The ECG computer of claim 1 wherein the sixth means is responsive to a number of SVE ectopic beats in the ECG information exceeding a predetermined number in a predetermined unit time for producing the control signals.
11. The ECG computer of claim 1 wherein the sixth means is responsive to the amplitude of the R-wave component of the ECG information exceeding a predetermined quantity for producing the control signals.
12. The ECG computer of claim 1 wherein the sixth means is responsive to the width of the R-wave component of the ECG information exceeding a predetermined quantity for producing the control signals.
13. The ECG computer of claim 1 wherein the sixth means is responsive to the premature appearance of the R-wave component of the ECG information by a predetermined amount for producing the control signals.
14. The ECG computer of claim 1 wherein the sixth means is responsive to paired ectopic beats in the ECG information for producing the control signals.
15. The ECG computer of claim 1 wherein the sixth means is responsive to a heart beat rate of the ECG information exceeding a predetermined rate for producing the control signals.
16. The ECG computer of claim 1 wherein the sixth means is responsive to a heart beat rate of the ECG information lower than a predetermined rate for producing the control signals.
17. The ECG computer of claim 1 wherein the sixth means is responsive to an elevation of the ST level of the ECG information greater than a predetermined level for producing the control signals.
18. The ECG computer of claim 1 wherein the sixth means is responsive to a depressing of the ST level of the ECG information below a predetermined level for producing the control signals.
19. The ECG computer of claim 1 wherein the ECG information contained on the recording medium also contains event markers which have been recorded in accordance with the actuation of an event marking system by the patient and wherein the sixthmeans is responsive to the event markers in the ECG information for producing the control signals.
20. The ECG computer of claim 19 wherein the event marker consists of a short burst of pulses and wherein the sixth means detects such short burst of pulses.
21. The ECG computer of claim 20 wherein the short burst of pulses consists of a predetermined number of pulses in a predetermined period of time and wherein the sixth means includes means for detecting the predetermined number of pulses in thepredetermined period of time.
22. The ECG computer of claim 1 additionally including eighth means coupled to the sixth means for inhibiting the sixth means for a first run of the recording medium at high speed to produce continuous trend outut signals from the beginning tothe end of the recording medium and for cycling the recording medium back to the beginning and for enabling the sixth means for a second run of the recording medium from the beginning to the end.
23. An arrhythmia computer for use in a dynamic multispeed ECG computer for reproducing ECG information contained on a recording medium recorded at a particular speed, including:
first means for moving the recording medium past a fixed predetermined readout position,
second means coupled to the first means for controlling the first means to move the recording medium at at least one selected speed appreciably greater than the particular speed to provide high speed playback of the recorded information,
third means located at the fixed predetermined readout position for reproducing the recorded information when the first means moves the recording medium to provide the high speed playback,
fourth means coupled to the third means and responsive to the reproduced information for detecting the presence of ectopic beats within the reproduced information in accordance with parameters selectable singly and in combinations and includingthe amplitude, width and prematurity of the R-wave portion of the ECG complexes within the ECG information, and
fifth means coupled to the fourth means for selecting singly and in combinations the parameters used as a basis for detecting the presence of ectopic beats.
24. The arrhythmia computer for use in the ECG computer of claim 23 additionally including sixth means coupled to the fourth means for varying the width parameter within a preselected range.
25. The arrhythmia computer for use in the ECG computer of claim 23 additionally including sixth means coupled to the fourth and fifth means for producing individual control signals in accordance with each of the individual parameters and acontrol signal in accordance with the selected combination of parameters.
26. The arrhythmia computer for use in the ECG computer of claim 23 wherein the fifth means provides for the individual selection of parameters for controlling the detection of VE ectopic beats and wherein the fourth means provides forpreselected parameters controlling the detection of SVE ectopic beats.
27. The arrhythmia computer for use in the ECG computer of claim 26 additionally including sixth means coupled to the fourth and fifth means for producing individual control signals in accordance with each of the individual parameters andindividual control signals in accordance with the selected combination of parameters for detecting VE ectopic beats and with the preselected parameters for detecting SVE ectopic beats.
28. The arrhythmia computer for use in the ECG computer of claim 27 additionally including seventh means coupled to the sixth means for producing individual control signals in accordance with a preselected activity of detected VE and SVE beats.
29. The arrhythmia computer for use in the ECG computer of claim 23 additionally including sixth means coupled to the fourth means for detecting the presence of paired ectopic beats.
30. The arrhythmia computer for use in the ECG computer of claim 29 additionally including seventh means coupled to the sixth means for producing a control signal in accordance with the detection of paired ectopic beats. .[.31. A recorder foruse with a dynamic multispeed ECG computer for reproducing ECG information contained on a recording medium recorded at a particular speed and with the ECG computer including first means for moving the recording medium past a plurality of fixedpredetermined readout positions and with the ECG computer including second means for controlling the first means to move the recording medium at a selected one of a plurality of speeds including the particular speed and including at least one speedappreciably greater than the particular speed, to provide real time and high speed playbacks respectively of the recorded information and with the ECG computer including third means located at a first one of the fixed predetermined readout positions forreproducing the recorded information when the first means moves the recording medium to provide real time playback and with the ECG computer including fourth means located at a second one of the fixed predetermined readout positions for reproducing therecorded information when the first means moves the recording medium to provide high speed playback and with the ECG computer including fifth means responsive to an event signal contained within the ECG information played back at high speed to controlthe second means to move the recording medium for real time playback for a predetermined period of time and then control the second means to return to a high speed playback, the recorder including:
a recording medium system for recording ECG information in response to input signals,
an event marker for producing an event signal, and
switching means coupled to the event marker and the recording medium system for controlling the recording of the event signal on the recording medium in response to the actuation of the switching means..]. .[.32. The recorder of claim 31wherein the event signal consists of a short burst of pulses..]. .[.33. The recorder of claim 32 wherein the short burst of pulses consists of a predetermined number of pulses in a predetermined
period of time..]. 34. A dynamic multispeed ECG computer for reproducing ECG information contained on a recording medium recorded at a particular speed, including:
first means for moving the recording medium past a plurality of fixed predetermined readout positions,
second means coupled to the first means for controlling the first means to move the recording medium at a selected one of a plurality of speeds including the particular speed of recording and including more than one speed appreciably greater thanthe particular speed to provide real time and high speed playbacks respectively of the recorded information,
third means located at a first one of the fixed predetermined readout positions for reproducing the recorded information when the first means moves the recording medium to provide real time playback,
fourth means located at a second one of the fixed predetermined readout positions for reproducing the recorded information when the first means moves the recording medium to provide high speed playback,
fifth means coupled to the fourth means and responsive to the reproduced signals at high speed playback for producing output signals in accordance with the trend of particular characteristics of the ECG complexes at high speed playback,
sixth means coupled to the fourth means and responsive to the reproduced signals for producing control signals upon the detection of predetermined characteristics of the ECG complexes,
seventh means coupled to the sixth means and the second means and responsive to the control signals produced by the sixth means for controlling the second means to move the recording medium at the real time playback speed for a predeterminedperiod of time upon the detection of the predetermined characteristis of the ECG complexes and to then return to the selected one of the multispeed high speed playbacks, and
eighth means coupled to the fifth, sixth and seventh means for inhibiting the production of the control signals by the sixth means during a first forward run of the recording medium from the beginning to the end to provide a continuous high speedtrend output, for immediately rewinding the recording medium to the beginnning, and for then enabling the production of the control signals by said sixth means during a second forward run of the recording medium from the beginning to the end in which therecording medium is run at the real time playback speed for a predetermined period of time upon the detection of the predetermined characteristics of the ECG complexes under control of said seventh means.
5. The ECG computer of claim 34 additionally including ninth means including a paper writer for reproducing the trend output signals and the paper writer operating at a speed to reproduce the trend output signals on a portion of the paper charthaving a length equal to a small fraction of the length of recording medium, and for reproducing the ECG signals and the paper writer operating at a speed to reproduce the ECG signals on a
portion of the paper chart on a real time basis. 36. The ECG computer of claim 35 wherein the fifth means produces trend output signals representing heart beat rate and ST level and wherein the paper writer provides a two channel writeout ofthe trend information on the trend
chart. 37. The ECG computer of claim 35 additionally including tenth means for producing a digital printout of time related to the time of recording
of the ECG signals on a real time basis. 38. The ECG computer of claim 35 wherein the sixth means is responsive to ectopic beats in the ECG information reproduced at high speed playback for producing the control
signals. 39. The ECG computer of claim 34 wherein the sixth means is responsive to VE ectopic beats in the ECG information for producing the
control signals. 40. The ECG computer of claim 34 wherein the sixth means is responsive to SVE ectopic beats in the ECG information for producing
the control signals. 41. The ECG computer of claim 34 wherein the sixth means is responsive to a number of ectopic beats in the ECG information exceeding a predetermined number in a predetermined unit time for
producing the control signals. 42. The ECG computer of claim 34 wherein the sixth means is responsive to a number of VE ectopic beats in the ECG information exceeding a predetermined number in a predetermined unit time
for producing the control signals. 43. The ECG computer of claim 34 wherein the sixth means is responsive to a number of SVE ectopic beats in the ECG information exceeding a predetermined number in a predetermined
unit time for producing the control signals. 44. The ECG computer of claim 34 wherein the sixth means is responsive to the amplitude of the R-wave component of the ECG information exceeding a predetermined quantity for
producing the control signals. 45. The ECG computer of claim 34 wherein the sixth means is responsive to the width of the R-wave component of the ECG information exceeding a predetermined quantity for producing the
control signals. 46. The ECG computer of claim 34 wherein the sixth means is responsive to the premature appearance of the R-wave component of the ECG information by a predetermined amount for producing the control
signals. 47. The ECG computer of claim 34 wherein the sixth means is responsive to paired ectopic beats in the ECG information for producing
the control switches. 48. The ECG computer of claim 34 wherein the sixth means is responsive to a heart beat rate of the ECG information exceeding
a predetermined rate for producing the control signals. 49. The ECG computer of claim 34 wherein the sixth means is responsive to a heart beat rate of the ECG information lower than a predetermined rate for producing
the control signals. 50. The ECG computer of claim 34 wherein the sixth means is responsive to an elevation of the ST level of the ECG information
greater than a predetermined level for producing the control signals. 51. The ECG computer of claim 34 wherein the sixth means is responsive to a depressing of the ST level of the ECG information below a predetermined
level for producing the control signals. 52. The ECG computer of claim 34 wherein the ECG information contained on the recording medium also contains event markers which have been recorded in accordance with the actuation of an event markingsystem by the patient and wherein the sixth means is responsive to the event markers in the ECG information for
producing the control signals. 53. The ECG computer of claim 52 wherein the event marker consists of a short burst of pulses and wherein the sixth
means detects such short burst of pulses. 54. The ECG computer of claim 53 wherein the short burst of pulses consists of a predetermined number of pulses in a predetermined period of time and wherein the sixth means includes means fordetecting the predetermined number of pulses in the
predetermined period of time. 55. In a dynamic multispeed ECG computer for reproducing ECG information contained on a recording medium recorded at a particular speed, including a first means for moving the recording medium at at least onefixed predetermined real time readout position and at least one fixed predetermined high speed readout position, a second means coupled to the first means for controlling the first means to move the recording medium at a selected one of a plurality ofspeeds including the particular speed and including more than one speed appreciably greater than the particular speed to provide real time and high speed playbacks respectively of the recorded information, a third means located at the fixed predeterminedhigh speed readoutposition for reproducing the recorded information when the first means moves the recording medium to provide high speed playback, a fourth means located at the fixed predetermined real time readout position for reproducing the recordedinformation when the first means moves the recording medium to provide real time playback, a fifth means coupled to the third means and responsive to the reproduced signals at high speed playback for producing output signals in accordance with the trendof particular characteristics of the ECG complexes at high speed playback, and a sixth means coupled to the third means and responsive to the reproduced signals for producing control signals indicative of the occurrence of the predetermined events withinthe characteristics of the ECG complexes, the improvement comprising:
seventh means coupled to the sixth means and the second means and responsive to the control signals provided by the sixth means for controlling the second means to move the recording medium at the real time playback speed upon the occurrence ofthe predetermined events within the
characteristics of the ECG complexes. 56. In an arrhythmia computer for use in a dynamic multispeed ECG computer for reproducing ECG information contained on a recording medium recorded at a particular speed and including a first means formoving the recording medium past a fixed predetermined readout position, a second means coupled to the first means for controlling the first means to move the recording medium at at least one selected speed appreciably greater than the particular speedto provide high speed playback of the recorded information, a third means located at the fixed predetermined readout position for reproducing the recorded information when the first means moves the recording medium to provide the high speed playback, theimprovement comprising:
fourth means coupled to the third means and responsive to the reproduced information for detecting the presence of ectopic beats within the reproduced information in accordance with parameters selectable singly and in combinations and includingthe amplitude, width and prematurity of the R-wave portion of the ECG complexes within the ECG information, and,
fifth means coupled to the fourth means for selecting singly and in combinations the parameters used as a basis for detecting the presence of
ectopic beats. 57. In a dynamic multispeed ECG computer for reproducing ECG information contained on a recording medium recorded at a particular speed and including a first means for moving the recording medium past a plurality of fixedpredetermined readout positions, a second means coupled to the first means for controlling the first means to move the recording medium at a selected one of a plurality of speeds including the particular speed of recording and including more than onespeed appreciably greater than the the particular speed to provide real time and high speed playbacks respectively of the recorded information, a third means located at a first one of the fixed predetermined readout positions for reproducing the recordedinformation when the first means moves the recording medium to provide real time playback, a fourth means located at a second one of the fixed predetermined readout positions for reproducing the recorded informatin when the first means moves therecording medium to provide high speed playback, a fifth means coupled to the fourth means and responsive to the reproduced signals at high speed playback for producing output signals in accordance with the trend of particular characteristics of the ECGcomplexes past high speed playback, a sixth means coupled to the fourth means and responsive to the reproduced signals for producing control signals upon detection of predetermined characteristics of the ECG complexes, the improvement comprising:
seventh means coupled to the sixth means and the second means and responsive to the control signals produced by the sixth means for controlling the second means to move the recording medium at the real time playback speed for a predeterminedperiod of time upon the detection of the predetermined characteristics of the ECT complexes and to then return to the selected one of the multispeed high speed playbacks, and,
eighth means coupled to the fifth, sixth and seventh means for inhibiting the production of the control signals by the sixth means during a first forward run of the recording medium from the beginning to the end to provide a continuous high speedtrend output, for immediately rewinding the recording medium to the beginning, and for then enabling the productin of the control signals by the sixth means during a second forward run of the recording medium from the beginning to the end in which therecording medium is run at the real time playback speed for a predetermined period of time upon the detection of the predetermined characteristics of the ECG complexes under control of said seventh means. |
| Description: |
The present invention relates to an electrocardiographic computer with visual display and in particular, to a computer for automatically processing large volumes of electrocardiac signals and for displaying and permanently recording ananalysis of these large volumes of signals in a relatively short period of time.
Electrical signals that circulate upon the surface of a person's skin as a result of the expansions and contractions of the cardiac muscle are known as ECG signals. These ECG electrical signals exhibit particular waveforms and the action of thecardiac muscle and the condition of the muscle produce waveforms with particular characteristic relationship. A well-known technique in the medical field is to place electrodes on the patient's skin so as to sense the ECG signals for visualpresentation. Many types of devices are currently available to provide the visual presentation of the ECG signal for viewing either in real time or for viewing at some subsequent time by a cardiologist or other trained personnel.
For example, it is possible to use a cathode-ray oscilloscope to provide for the presentation of the ECG signal either directly from the patient in real time, or at a later time from a recording of the ECG signals using a recording device such asa magnetic tape recorder. In addition, the ECG signals may be recorded by a paper writer on paper tape which is called an electrocardiograph. The graph may be subsequently viewed by trained personnel for a determination of the characteristics of thewaveforms. All of these above methods provide for a fairly limited analysis of the ECG signals since the signals are generally monitored for a relatively short period of time and do not provide for the monitoring of the characteristics of the ECGsignals over a long period of time, which period of time should include the normal activities of the patient.
A more desirable method of analyzing ECG signals is to accumulate large volumes of such signals and with the accumulation of the signals occurring while the patient is engaged in his normal activities. Since it would be impossible to analyzesuch recorded signals on a one-to-one time relationship because of the long recording period, the subsequent presentation of the ECG signals must be at an accelerated rate. Electrocardioscanner.RTM.type of analysis is accomplished by recording the ECGsignals in real time on a small compact tape recorder which is worn by the patient who is instructed to engage in his normal activities. The recorded ECG signals are then processed by replaying the signals at a much faster speed and with a presentationof the ECG signals on a cathode-ray oscilloscope, and with each ECG complex superimposed on the predecessor complexes. This type of superimposed replay in fast time is known as an AVSEP.RTM. display and has been registered under the trademarkAVSEP.RTM. and Electrocardioscammer.RTM. . As a particular example of a system which may be used for the recording and playback of ECG signals with the recording in real time and with the playback in fast time, reference is made to U.S. Pat. No.3,215,136, issued Nov. 2, 1965, in the name of Norman J. Holter, et al.
In the prior art ECG scanning device disclosed in U.S. Pat. Ser. No. 3,215,136, the superimposition of the ECG signals is accomplished by recording the same ECG signal on two different tracks of a magnetic recording tape, but with the samesignals on the different tracks longitudinally displaced. The playback of the ECG signals is accomplished by using spaced magnetic playback heads for reproducing the ECG signals on the two tracks. A first one of these playback heads reproduces the ECGsignals on a first one of the tape tracks for the purpose of producing a trigger signal while the second one of the playback heads reproduces the ECG signal on a visual indicator such as an oscilloscope.
The two playback heads reproduce the information which is longitudinally displaced on the two tracks so that the trigger signal which is generated from the first track synchronizes the horizontal sweep of the oscilloscope so that each ECG traceon the oscilloscope is initiated at the same point in the ECG complex. In this way each ECG trace is displayed in its entirety.
The prior art devices for providing the superimposed display as described above are capable of processing and providing a presentation of data from only one pair of ECG leads attached to the patient and these prior art devices are capable of highspeed playback at only one speed. The prior art electrocardioscanning system such as shown in U.S. Pat. No. 3,215,136 have proven to be of invaluable assistance to the cardiologist for the determination of the presence and characteristics of certainabnormalities even in view of the limited nature of the device as described above.
As an extension of the prior art ECG scanning device described above, an improvement as shown in U.S. Pat. No. 3,718,772, issued Feb. 27, 1973, in the name of Clifford Sanctuary, provides for the reproduction of ECG signals from a single trackmagnetic tape recorder. Specifically, that reproducing system provides for recording at a very slow speed on a single track and then playing back at a high speed with provisions for the superimposition of the ECG complexes on a visual indicator such asan oscilloscope. Trigger signals to control the horizontal sweep are developed by the reproduction from the single track using a first playback trigger head. The trigger signals are delayed a particular period to provide for delayed trigger signalswhich control the sweep of the oscilloscope. This produces a stable superimposition of the ECG signals since the ECG signals are reproduced by a second playback head spaced from the first playback head. In this system, data is obtained from only onepair of ECG leads attached to the patient.
A further extension of the prior art is shown in U.S. Pat. application Ser. No. 430,704 now U.S. Pat. No. 4,006,737, issued Feb. 8, 1977 to Cherry and assigned to the assignee of the present invention, for an improved ECG scanning devicefor processing and observing large quantities of ECG signals in a relatively short interval of time, and in particular for providing an analysis of these large quantities of ECG signals. The scanning device of Ser. No. 430,704 provided for theprocessing and simultaneous presentation of ECG data from at least two pairs of leads located in different positions on the patient. Since more than one pair of ECG leads attached to the patient provided the cardiologist with different views of the samecardiac activity, the simultaneous presentation of the ECG information from at least two pairs of leads provided the cardiologist sufficient information to recognize an abnormality not obvious when viewing information obtained from a single pair ofleads.
In order to increase the flexibility in the analysis of data with the ECG scanning device of the device of Ser. No. 430,704, the scanner was capable of playback not only in real time, but also at multiple high speed playback speeds. Forexample, the prior art device provided for playback speeds of 30, 60 and 120 times real time. The highest of these playback speeds was twice that previously obtained so as to provide for an obvious savings of time during the analysis of the superimposedinformation. The lowest of these high speeds was one-half the speed of that previously used to provide a slower presentation of the superimposed ECG complexes to allow better visual analysis of the recorded ECG information at critical time. Also, thisslower playback speed allowed for the ECG signal to be connected to an external digital computer and with the information occurring at a slow enough rate so that the computer digitized the information with high resolution.
In order to achieve multiple high speed playback speeds and still provide realistic waveforms from the processed ECG information, the device of Ser. No. 430,704 included improvements in the tape deck and the circuitry associated with the tapedeck to provide for proper performance. For example, the playback amplifiers had specific amplitude and frequency responses which were logically switched upon the selection of a particular playback speed so as to provide for accuracy in the reproducedECG information. A variable tapedeck delay loop was used in combination with two spaced playback heads so as to provide a variable reaction time for manually switching from viewing superimposed ECG complexes at a selected high speed to a real timereproduction on a paper writer of the previously viewed ECG complexes. This was accomplished without the necessity of backing up the tape on the tape playback deck.
The device of Ser. No. 430,704 included a digital clock which was not only used to provide a visual indication of the time of day, but was also used to provide digital outputs of the time of day to the paper writer or any other external device. The digital clock might also be used to provide time synchronization of the processed data for use by external devices such as computers, paper writers, etc.
The device of Ser. No. 430,704 also included a heartbeat totalizer for providing a digital display of the number of heartbeats recorded on the magnetic tape. This heartbeat totalizer could provide either a display of the total number ofheartbeats recorded on a complete tape, or could provide a display of the hour-by-hour total of the heartbeats. This digital display of either the total number of heartbeats or an hour-by-hour number of heartbeats was provided with the magnetic tapeplayed back in either real time or at 30, 60 or 120 times real time or when the tape is moved in Fast Forward or Fast Reverse. In order to insure that the heartbeat totalizer is accurate, the device of Ser. No. 430,704 provided means to subtractheartbeats from the total when the tapedeck was in Fast Reverse. This allowed the identification and location of specific ECG complexes by number. The heartbeat totalizer also produced output signals of total beats or hour-by-hour beat totals for anexternal display such as a paper writer.
The device of Ser. No. 430,704 also provided an arrhythmia computer to detect and digitally display the numbers of premature ventricular contractions (VE) and supraventricular ectopic beats (SVE). The arrhythmia computer detected the VEs andSVEs from the magnetic tape at playback speeds of 30, 60 and 120 times the recorded speed. The arrhythmia computer provided either a display of the complete total or a display of the hour-by-hour total of the arrhythmia occurrences described above. Inaddition, the arrhythmia computer was designed to actuate event markers on a paper writer when the arrhythmia occurrences exceeded preselected number of occurrences during a predetermined time interval. In addition, the arrhythmia computer provided fora digital printout of the hour-by-hour totals of the arrhythmia occurrences.
The various printouts on the paper writer described above, plus novel trend data, which was analyzed from the recorded magnetic tape, was used with a multispeed multichannel, paper writer for reproducing analog data, digital printed data andevent marking. This multichannel paper writer had the capability of writing two tracks of ECG data from the magnetic tape which had been recorded in real time and with the writing occurring at either of two writing speeds. The two tracks of ECG datafrom the magnetic tape were used at high speed playback to provide two channels of trend data. These two channels of information could be the heart rate and the ST segment level so as to provide for a scanning of an entire 24 hour tape in a period asshort as 12 minutes. The paper writeout of the two channels of data, representing the heart rate and the ST segment level for the entire 24 hour period was provided on a relatively short piece of paper and was provided in the short time period such as12 minutes. The paper writer also included the displaying of digitally printed data such as the time of day, arrhythmia and heartbeat totalization from signals generated in the ECG computer. The paper writer also provided for the automatic control ofthe paper speeds during the trend analysis so as to provide constant paper speed versus recorded time, even with different playback speeds. In addition, the paper writer could be rapidly switched from the high speed trend analysis to low speed ECGwriteout with automatic control of the various parameters and responses.
The present invention is an extension of and, an improvement of the Electrocariographic Computer Device disclosed in Ser. No. 430,704. Specifically, the present invention includes recording two tracks of information on a miniature recorderwhich includes a built-in clock with a visual display. The recorder also includes an event marker, which may be activated when the patient experiences a predetermined event. For example, when the patient experiences some unusual heart activity orundergoes a predetermined physical activity or any other unusual occurrence, the patient pushes a button on the miniature recorder which momentarily interrupts the recording of information in one of the two tracks to record in place of the information apulse burst as an event marker. At the same time, the patient may look at the visual time display and record on a log sheet the time and the nature of the event.
During playback, the present invention provides for a much greater degree of automatic processing of the tape so that the monitoring of the tape may be accomplished without the necessity of a technician visually observing the oscilloscope ormonitoring an audible representation of the ECG signals. For example, during playback the computer may be set to provide a trend run so as to print out the trend analysis for the beginning to the end of the tape and then have the tape stoppedautomatically. Thereafter, the computer can be set to automatically cycle to the beginning of the tape to again print out the trend analysis, but with an automatic detection of various events. The detection of the various events are used to trigger thecomputer so that the tape is slowed down to real time to print out the portion of the ECG signals during the event. In other words, the technician does not have to monitor the playback to manually slow the tape down to real time as was done previously,but the computer itself senses the occurrence of an event during trend and slows the tape down to print out in real time the ECG signals and then speeds back up to the originally selected trend speed.
The present invention provides for the slow down to real time write-out during the trend analysis with the occurrence of events such as the occurrence of the event marker on the tape which has been placed there by the action of the patient. Inaddition, the computer may automatically detect the occurrence of an unusual event within the ECG signals to control the real time write-out. For example, the event may be various ectopic beats such as VEs or SVEs, an unusual level for the ST level, arapid heart beat or a slow heart rate and any other unusual event which it may be desired to program into the computer.
In order to facilitate the control of the desired events which may be used to slow down the computer to real time, the arrhythmia computer may have a greater flexibility than the prior art arrhythmia computers. Specifically, the arrhythmiacomputer of the present invention allows for the selection of one or a number of parameters so that the operator has complete control as to what is to be the parameters of arrhythmia detection. For example, the operator can select such parameters aspaired beats, degree of prematurity, width and amplitude. Any one of any combination of these parameters, may be controlled by the operator to provide for the event which will trigger the computer to slow down and print out the ECG signals in real time.
A clearer understanding of the present invention will be had with reference to the following description and drawings wherein:
FIG. 1 illustrates an isometric view of an improved dynamic electrocardiography computer of the present invention, showing the front panel and the tapedeck and including a plurality of digital output indicators, an oscilloscope display, a paperwriter, and an automatic computer control panel.
FIG. 1(a) illustrates a detail of the panel of FIG. 1 and specifically shows the automatic computer control panel.
FIG. 2, includes FIGS. 2, 2' and 2" which when positioned side-by-side constitute a block diagram of the tapedeck control logic circuit for providing control of the tape deck at various speeds and in various directions in accordance with keyboardactuations.
FIG. 2(a) illustrates, in more detail, the brake logic circuit shown in FIG. 2.
FIG. 3 illustrates a schematic of the relay and motor interconnections to provide control of the motor at various speeds.
FIG. 4 illustrates the recorder to record ECG signals and including an event marker.
FIG. 5 illustrates a block diagram of the event mark pulse generator included in the recorder.
FIG. 5(a) are waveforms used in explaining the operation of the event mark pulse generator of FIG. 5.
FIG. 6 illustrates a schematic of the compensated head amplifiers for playback in real time and at multiple high speed playbacks.
FIG. 7 illustrates the tape loop path from the supply reel to the tape reel and including a variable delay loop.
FIG. 8 illustrates a block diagram of the autoscan, autostop system.
FIG. 8(a) illustrates the cycling of the tape during autoscan or autostop.
FIG. 9 illustrates a block diagram of a playback decoder for decoding the event mark from the high speed ECG signals.
FIG. 9a illustrates a typical write out of real time information during auto-scan.
FIG. 10 illustrates the optical encoder for use in providing a clodk signal in accordance with tape movement, and
FIG. 10(a) are waveforms used in explaining the operation of the optical encoder of FIG. 10.
FIG. 11 is a block diagram of the digital clock and including the clock display.
FIG. 12 illustrates a typical trend chart writeout including event markers and digital information.
FIG. 13 illustrates a typical auto-scan chart writeout including trend information and real time information.
FIG. 14 illustrates a block diagram of the paper writer control system.
FIG. 15 illustrates a block diagram of a heart rate trend system to produce a trend output for the paper writer and event signals for the auto-scan
FIG. 16 is a block diagram of an ST level system to produce a trend output for the paper writer, and event signals for the auto-scan
FIG. 17 illustrates the front panel of the arrhythmia analyzer.
FIG. 18 illustrates a block diagram of the arrhythmia analyzer for supplying signals to the front panel shown in FIG. 17 and to the paper writer, and to the computer auto write.
FIG. 18(a) illustrates a block diagram of the paired beat detector of FIG. 18.
FIG. 18(b) are waveforms used in explaining the operation of the paired beat detector of FIG. 18(a).
FIG. 19 illustrates a typical ECG complex as compared with an ECG complex with a wide QRS segment.
FIG. 20 illustrates a typical ECG complex as compared with ECG complexes having abnormalities in the amplitude of the QRS segment.
FIG. 21 illustrates a block diagram of a heartbeat totalizer including a heartbeat totalizer display.
The present invention is an improvement of the electrocardiocomputer disclosed in application Ser. No. 430,704 and the disclosure of Ser. No. 430,704 is incorporated herein by reference.
in FIG. 1, an improved electrocardiocomputer ofthe present invention is shown. This computer provides for two channel playback of superimposed high speed ECG complexes and an arrhythmia bar graph all in the same oscilloscope display section 10. A two channel paper writer 12 includes in addition tothe two channels of information, a plurality of event markers and a digital writer 14, to print digital information. In addition to the oscilloscope and paper writer, various digital displays are provided on the front panel, which include a digital timeclock 16, an arrhythmia analyzer 18, and a heartbeat counter 20. An audio output may be provided by a speaker 22.
The various displays are controlled by control knobs and switches located adjacent to the display. For example, control sections 24 and 26 control the gain and polarity of the two channels of ECG information. Control section 28 controls thetrigger delay for the sweep of the superimposed ECG complexes and also controls the speed of the sweep to widen the trace. The scale of the arrhythmia bar display is controlled by control section 30. A control section 32 varies the input amplitude ofthe signal from the recorder. The input from the two channels of the recorder may be connected directly into the input jacks in section 34 in order to provide for a recorder test.
The paper writer 12 may also include controls such as controls 36 and 38 to vary the sensitivity of the paper writer in the two channels. The paper speed may be controlled by a group of push buttons 40.
The digital time clock includes setting buttons 42 to set the time and setting buttons 44 to set either AM or PM. The arrhythmia analyzer includes switches 46 to control a predetermined number of events per minute to be exceeded, and a swtich 48to control the totalizing either in an hour period or cumulatively. The ST level trend computer includes an ST delay control 50. The heartbeat computer includes a switch 52 for either one hour totals or cumulative totals.
The tape transport section 54 includes a variable delay tape loop 56 and an adjustment switch for different reel sizes 58. In addition, the master panel includes a plurality of push buttons 60 to control the tape speed and direction. Aplurality of push buttons 62 control the paper writer to provide different output writing modes. A series of push buttons 64 provide a control of the oscilloscope display. The reel size switch is included in an automatic computer control panel 66divided into a recorder section 68, a playback section 70, a computer auto write section 72 and a tapedeck section 74.
FIG. 1(a) illustrates in greater detail the automatic computer control panel 66 including recorder section 68 playback section 70, computer auto write 72, and tape deck section 74. Tape deck section 74 includes the reel size switch 58 which isused to provide for adjustments in accordance with the reel size of the tape used with the ECG computer of the present invention.
The recorder section 68 includes a switch 76 which is positioned in accordance with the speed in which the recorder recorded the ECG signals. For example, the prior art recorders recorded the information at a speed such as 1/8 inch per second. In order to maximize the recording time and minimize the size of the recorder, the present inventiom may operate with a recorder that records information at half that speed, such as 1/16 inch per second. In order to compensate for this lower recordingspeed and allow the ECG computer to service all prior art recorders the switch 76 may be positioned either at a full speed position or a half speed position. In the half speed position of switch 76 the real time playback is at twice the speed as before,so that the size of the real time playback head need not be increased. The ECG computer must have the other controls designed so that the playback, although at twice the speed, appears to be at real time or at a preselected multiple of real time. Forexample, the paper recorder can be run at twice the speed as before and the other portions of the computer operated so as to compensate for the increase in the playback speed of the recording tape. The recorder section 68 also includes a tapecompensation switch 78 which has three positions which are set in accordance with needed compensation of the recording tape in accordance with the original recording speed and other factors.
Play back section 70 includes an autostop on-off switch 80, an auto-scan on-off switch 82 and an auto-write rotary switch 84. The autostop switch 80 controls the playback during trend to automatically stop the tape at the end of a trend run. The auto-scan switch 82 controls the computer to cycle the trend analysis back to the beginning of the tape and then allows an automatic scan of the tape at high speeds with periodic reduction to real time write out in accordance with particular events. The auto-write rotary switch 84 provides an adjustment for the amount of real time write out each time the tape is automatically reduced to real time in accordance with the detection on an event.
The computer auto-write section 72 includes a switch 86 which controls the tape during auto-scan to write out in real time upon the occurrence of a single VE event. Switches 88 and 90 provide for automatic write outs in real time upon theoccurrence of multiple Ve or SVE events, in accordance with preselected parameters, set by the arrhythmia analyzer 18. An on-off switch 92 controls the auto-scan write out real time in accordance with detection of an event burst which has been placed onthe tape by the patient upon the activation of the event button. In addition to the switches 86, 88, 90 and 92, any number of additional event switches may be incorporated such as switches 94 and 96 to control the auto-scan to write out real time ECGsignals, in accordance with events such as a heart rate event or an ST level event. In addition, other specific events which may be included to control auto-scan write out will be gone into in greater detail at later portions of the specification.
It is to be appreciated that the above description of the overall outward appearance of the ECG computer of the present invention is general in nature and in many instances, more specific details will be included at a later portion of thisspecification. For example, not every control element has been described and some elements which have been described are self-evident and conventional in their operation and may not be described in much greater detail.
Generally, the improved ECG computer of the present invention is a high speed ECG scanning device that documents abnormalities from a long term ECG recording such as a recording over a 24 hour period using two pairs of leads to provide twochannels of ECG information. This ECG information may be displayed in superimposed form at 30, 60 or 120 times real time, or as normal ECG traces in real time on the display oscilloscope 10. This display oscilloscope 10 provides a single multiscandisplay to provide both ECG traces an an arrhythmia bar trace simultaneously on the same cathode-ray tube.
The digital time clock 16 accurately displays tape time and relates it to the time of recording when preset at the start of the tape. A two channel paper writer 12 provides documentation of the ECG data being reviewed in the ECG real time mode. The time of day of each selected paper writeout is automatically printed on the electrocardiograph paper.
In addition to the writeout of the ECG data, the ECG computer includes specific analysis sections 434 and 432 to obtain heart rate and St segment data and event data from either of the ECG lead positions. This data is fed to the paper writer 12when the tape is programmed to be in the high speed mode to provide a trend chart of heart rate and ST segment in as little as 12 minutes from a 24 hour recording and to provide an auto-scan showing trend and real time data in accordance with eventdetection.
The heartbeat counter 20 provides the total number of heartbeats which occur either on an hour-by-hour basis or on a cumulative basis. The arrhythmia analyzer 18 provides digital displays of the numbers of ventricular and supraventricularectopic beats that occur on either a per-hour basis, or on a cumulative basis and also provides event data. This data may also be recorded digitally on the paper writer by the digital writer 14 and the event data may be used to control the auto-scanbetween high speed and real time write out.
As shown in FIG. 1, a group of push button switches are shown at position 60 to control the operation of the tapedeck. FIG. 2 illustrates these same push buttons for use in controlling the tapedeck control logic system. The push button switchesare momentary contact typewriter-type keys, which include built in indicators so as to provide a memory visual display of the present keyboard state. The push buttons are labeled, "Stop," "X1," "X30," "X60," "X120," "Fast Forward," and "Fast Reverse."The Stop key does not have an indicator lamp. The general operation of the control of the tapedeck in accordance with the particular key activated and with reference to FIG. 2, is as follows:
In the Stop mode, the tape does not move, but one of either motors M103 or M104 has torque to pull the tape. The other one of the motors M103 or M104 acts as a DC dynamic brake to hold the tape in a Stop position. The motor which acts as a DCdynamic brake is controlled to provide a force slightly larger than the takeup torque value. Either of the motors M103 or M104 may act as the brake, depending on the previous running state of the tape transport. For example, if the previous state wasfast forward (FF) or playback at any speed, then after the stop button is operated, the torque remains on the fast forward motor M104. If the previous state was fast reverse (FR), then after the stop button is operated, the torque would remain on thefast reverse motor M103, and the brake would be provided by the fast forward motor M104. The above described system provides a tape-tensioning design to keep the tape tight around the tape loop at all times. It is especially important that the tape istight around a clock pulley 100 which pulley is used to drive an optical encoder to produce a clock time signal.
In the X1, or real time mode, the X1 capstan roller R102 is controlled by the X1 capstan solenoid S102 to move towards the magnetic tape and engage the X1 motor capstan C102. In this mode, the fast forward motor M104 is operated at low torqueand the fast reverse motor M103 acts as a dynamic brake.
In the X30, X60 and X120 high speed playback modes which are 30, 60 and 120 times real time, the high speed capstan roller R101 is activated by the high speed capstan solenoid S101 to move toward the magnetic tape and engage the high speedcapstan C101. The fast forward motor M104 is operated at a higher torque than in the X1 mode. The fast reverse motor M103 acts as a dynamic brake, but at a lower value than in the X1 mode, since the supply reel of tape 200 is moving at a greatlyincreased speed. By activating the desired one of the X30, X60 or X120 keys, the speed of the high speed capstan motor is controlled to operate either at 900, 1,800, or 3,600 rpm.
In the Fast Forward and Fast Reverse mode, a large torque is applied to the applicable motor and with a small dynamic brake to the other one of the motors. This keeps the tape tight during starting and fast rewind, so that the tape does not sliparound the digital clock pulley 100. If the direction of fast rewind is changed from fast forward to fast reverse, or from fast reverse to fast forward, the torque and dynamic brake are also reversed, so that the tape reverses direction without throwinga tape loop. The tape first stops slowly, then increases in speed since the motors are controlled to always have one reel pulling and one reel holding back independent of the direction of tape travel.
In order to change from one mode to another, the logic design of FIG. 2 is designed to provide rapid mode changing from any condition without a tape loop or loss of tension. This is important, since a loss of tension around the clock pulley 100would cause time errors. To achieve this, the design has certain automatic features that prevent particular conditions from occurring. For example, during rapid fast forward tape travel, it is impossible to activate the X1, X30, X60 or X120 keyboardswitches. Such an activation would cause a tape foul-up, since the tape would still be moving at a high speed and depending upon the reel size, and the amount of tape on the reel, the normal inertia may keep the reel moving several seconds. This wouldbe true for either Fast Forward or Fast Reverse mode, so that the system of FIG. 2 includes memory circuits that make the tapedeck automatically go to a Stop mode if any other key such as X1, X30, X60 or X120 is activated after a Fast Forward or FastReverse mode.
As indicated above, the system is specifically designed to keep adequate tape tension around the digital clock pulley 100 under all possible modes of operation or changes from any mode to any other mode. This it to insure that the pulley 100accurately moves in relation to tape movement to provide for a reliable indication of the time of day relative to the tape position once the initial starting time for the tape has been preset.
As shown in FIGS. 1 and 2, a rotary switch 58 is used to adjust the take-up torque for operation in either Fast Forward or Fast Reverse and also adjust the dynamic brake used in stopping the tape and in the playback of the tape for reel sizes of13/4, 3, 4 and 7 inch.
Turning specifically to FIG. 2, the motor M101 is a three speed synchronous motor that runs at either 900, 1,800, or 3,600 rpms by connecting poles in the motor in different configuratins. This type of motor is commercially available and onesuch motor which is available bears model number NCH-13, B7122XZ, 115V, 50/60 HZS, 900/1800/3600, and is manufactured by the Bodine Electric Company of Chicago, Illinois. This motor uses a total of 7 input wires and by varying the connection to theseinput wires, gives the three desired speeds of 900, 1,800 and 3,600 rpms. The motor, M101, is connected through a pulley P101 and a drive belt B101 to drive the high speed capstan configurations. to as to provide tape speeds of 33/4, 71/2 and 15 inchesper second. The X30, X60 and X120 push buttons change the logic circuit L1 to provide output signals to two relays K1 and K2, which in turn provide the proper connections to the motor M101 to produce the three seeds. Motor M101 is controlled to alwaysrun at one of its three speeds and may then be changed to any other speed. Since the motor is always maintained at its last operational mode speed, a fast transfer may be made to any other speed since the motor is already moving and does not have to bestarted from a rest position. The speed modes may therefore be rapidly changed with minimum delay to provide very rapid analysis between a high speed superimposed scan and a low speed X1 writeout.
The motor M102 is used to drive the tape at X1 speed and uses a capstan C101. The X1, or real time speed of the tape is 71/2 inches per minute which provides for the recorded tape containing information for a long period of time, such as 24hours. As indicated above, the two motors M103 and M104 provide fast reverse and fast forward functions.
The fast playback motor M101 generally provides for the three different playback speeds of X30, X60 and X120, by the use of an 8 pole motor and by choosing either two, four or eight poles within the motor to provide the different speeds ofrotation. The keyboard switches, X30, X60 and X120 provide momentary signals which activate the logic block L1 to set it in any one of three states. In addition, as shown in FIG. 2, reset inputs from any of the other keyboard contacts shown in FIG. 2return the logic L1 to the initial state.
As indicated above, the drive motor M101 is commercially available and includes 7 input wires designated W1 through W7. The specific interconnection of the AC line voltage by the relays K1 and K2 to the wires W1 through W7 is shown in FIG. 3. The relays K1 and K2 are controlled by signals from the logic block L1. The relays K1 and K2 in combination provide multipole double throw contacts to insure rapid switching from one speed to another without the use of rotary selectors. Specifically,the desired output speed for the motor M101 is obtained by the interconnection of the windings W1 through W7 using four pole double throw contacts. The logic block L1 controls the relays K1 and K2 in the following relationship and where the speed "S" atthe different high speed playback speeds is as follows:
S X30 = K1 .multidot. K2
S X60 = K1 .multidot. K2
S X120 = K1 .multidot. K2
FIG. 3 specifically shows the interconnection of the 7 wires, W1 to W7, to the multipole contacts controlled by the relays K1 and K2. At the X120 speed, one side of the AC line is connected to windings W1 and W4, the other side of the AC line isconnected directly to winding W6 and the other side of the AC line is connected through the starting capacitor C1 to winding W7. The capacitor C1 is used to apply starting torque to the motor M101. With this interconnection the motor operates as a twopole motor at 3,600 rpms. At the X60 speed, one side of the line is connected directly to the windings W1 and W2 and the other side of the line is connected directly to the winding W4 and through the starting capacitor C1 to the winding W5. With thisinterconnection the motor operates as a four pole motor at 1,800 rpms. At the X30 seed, one side of the AC line is directly connected to winding W1 and the other side of the AC line is connected directly to the winding W2 and through the capacitor C1 towinding W3. The motor now operates as an eight pole motor at 900 rpms.
The motors M103 and M104, shown in FIG. 2, are used to transport the magnetic tape in either direction during the Fast Forward or Fast Reverse commands. The motor M104 is also used to drive the tape take-up reel during the normal Play mode. During Fast Forward, or Fast Reverse, the two capstans C101 and C102 are not activated. A relay K3 is activated in the Fast Reverse mode to apply the line voltage to the motor M103. At this time, dynamic braking is applied to the motor M104 to keep thetape tight across the heads and around the clock pulley 100.
In the Fast Forward, or Play modes, at either the X1, X30, X60 or X120 speeds, AC line voltage is applied to the motor M104, using relays K4 and K5 and in accordance with the position of the reel size switch 58. As shown in FIG. 2, the reel sizeswitch 58 varies the voltage input in predetermined increments in accordance with a group of resistors. The relays K4 and K5 are used to short out the resistors R1 and R2 so as to drop the AC voltage to different levels to provide different takeuptorques. For example, a torque level "A" allows Fast Forward or Fast Reverse operation with relays K4 and K5 activated. A torque level "B" which is slightly lower is used during high speed playback at the X30, X60 and X120 speeds and is provided onlywhen relay K5 is activated. A torque level "C" is used to provide a take-up torque for the X1 mode or the Stop mode and is provided when neither of the relays K4 and K5 is activated.
The control logic system for the tape transport is shown in FIG. 2 as a plurality of logic blocks L1 to L10. Each logic block is formed from a plurality of conventional logic gates and flip-flops. It is to be appreciated that theinterconnection of these logic gates and flip-flops to form logic blocks L1 through L10 is of conventional design and will generally be described using logic equations. These equations are fully representative of the particular functions of these blocksand since the specific design of the logic blocks in and of themselves form no part of the invention, these equations and other descriptions are used to avoid excessive length in the description of the present invention.
The logic blocks L1, L2, L3, L4 and L5 are connected to the 7 push button switches shown in FIG. 2 and with each logic block including a flip-flop memory so as to hold the last state of operation. In addition, each of the 7 push buttons resetsthe other logic blocks so that any condition may be maintained.
As indicated above, the logic block L1 decodes the X30, X60 and X120 buttons to activate relays K1 and K2 to achieve the three motor speeds from the motor M101.
Logic blocks L3 and L6 work in combination with the keyboard inputs "Fast Forward" and "Fast Reverse" and "X1" and "Play" (where play = X30 + X60 + X120) to control relays K4 and K5. The operation of the relays K4 and K5 control the take-uptorque "T" at three levels "A," "B," or "C," of either the fast forward or fast reverse motors. The three levels of torque described above follow the logic equations,
Torque A = FF + FR = K4 .multidot. K5
Torque B = (Play X30 + X60 + X120) = K4 .multidot. K5
Torque C = Stop + X1 = K4 .multidot. K5
The logic block L5 is a simple set-reset flip-flop which stops the tape motion by resetting all other logic groups, releasing the capstan pressure roller, setting up the condition for the low torque level torque "C" on either the fast forward orfast reverse motor and increasing the DC dynamic brake on the supply motor.
The logic groups L2 and L4 determine the status of the high speed capstan C101 and the low speed capstan C102 and provide outputs to the applicable capstan drives D1 and D2. These capstan drives D1 and D2 in turn drive the high speed capstansolenoid S101 to activate the high speed capstan roller R101, or to drive the X1 capstan solenoid S102 to activate the X1 capstan Roller R102. the logic equations provided by logic groups L2 and L4 in accordance with the activation of particularkeyboard inputs are as follows:
Play = D1 + (X30 + X60 + X120) I
X1 = D2 .multidot. I where
I = Inhibit after FF and FR
An inhibit signal I from logic group L10 and flip-flop FF1 is also applied to logic groups L2 and L4 so as to prevent the capstan solenoids from being applied immediately after the tape is moving at high speed in either the Fast Forward or FastReverse mode. If either of the capstans were activated while the tape was traveling at high speed, tape breakage could occur. The inhibit signal I is formed from the memory flip-flop FF1. Specifically, the memory flip-flop FF1 is set to one stateafter either a Fast Forward or Fast Reverse operation and may only be reset by the activation of the Stop mode. Therefore the tape transport may only go to a Stop mode after a Fast Forward or Fast Reverse mode to thereby prevent damage to the tape.
The logic block L9 receives Fast Forward, Play and Fast Reverse keyboard inputs to control the flip-flop FF2 and the relay K3. The relay K3 is a reversing relay so as to control which one of the motors M103 and M104 is used to provide torque andwhich one is used to provide brake.
If TM103 = Motor M103 in Torque
TM104 = Motor M104 in Torque
BM103 = Motor M103 in Brake
BM104 = Motor M104 in Brake,
then,
TM103 = FR = K3
TM104 = FF + Play + X1 = K3
BM103 = TM103
BM104 = TM104
Logic group L7 in combination with the fast forward and fast reverse inhibit signal I from FF1 and in combination with the play logic L2 and the X1 logic L4 is used to provide an automatic stop feature. For example, if improper operationalprocedures are followed, wherein any one of four keys if depressed (X1, X30, X60 or X120) after the Fast Forward or Fast Reverse mode, then an automatic Stop mode is initiated as defined below.
I = Inhibit after FF and FR
AS = Auto Stop = (X1 + X30 + X60 + X120) I
In order to stop the motion of the tape, move the tape smoothly at the various speeds, and to hold the tape tight when stopped, the system of FIG. 2 includes dynamic and static braking. This braking is accomplished using a DC current from acurrent source which is applied to the windings of the AC torque motors M103 and M104. The current is switched from the output of the dynamic brake logic block L9 by the relay K3 to either one of the motors M103 or M104. The brake output circuitincludes an emitter follower Q1 as shown in FIG. 2A which is capable of high current output. This current when passed through an AC torque motor causes the rotor to drag due to eddy currents and magnetic hysteresis and the current is of sufficientmagnitude to perform high speed braking even for the large reels of tape. A reduced amount of braking current is used during the normal play operation or when the tape transport is in a Stop mode.
The operation of the braking circuit is that one of the motors act as a brake while the other motor acts as a take-up motor to provide that tape tension is always maintained during any mode or during a change from any mode to any other keyboardmode. This insures that the digital clock pulley 100 accurately follows the movements of the tape. Sufficient tension around the clock pulley 100 is maintained during rapid starting, rapid reversing, normal play speeds of X1 through X120, changingspeeds from X1 through X120, and during rapid stopping.
The logic blocks L8 and L9 obtain either speed or mode data from the various keyboard entries and logic outputs. In addition, the reel size switch 58 also is used as an input to the logic block L9 to control the amount of braking duringdifferent modes of operation. The output of the logic block L9 sets up the following braking conditions where:
BA = Brake to Stop after FF and FR
BB = Brake on X1 speed
BC = Brake on X30 speed
BD = Brake on X60 Speed
BE = Brake on X120 speed
BF = Brake on FF and FR
The amount of braking required during the movement of the tape at the X1, X30, X60 or X120 speed is different due to factors of friction and due to the effectiveness of the hysteresis braking of the motors M103 and M104 and therefore the amountof braking must be varied for each speed. The different braking factors is accomplished by applying different voltages to the emitter follower Q1 shown in FIG. 2A which in turn controls the flow of current to the appropriate motor. The differentbraking modes provided by the system of FIGS. 2 and 2A are as follows:
In the BA braking mode, maximum DC current flows through the supply motor which is either M103 or M104, depending on tape direction. This maximum DC current causes rapid tape stoppage without losing tension of the tape. The final value ofbraking exceeds the take-up torque of the take-up motor and therefore the tape stops and remains under tension.
In the BB through BE braking modes different brake values are supplied to the motor M103 to keep the proper amount of tension on the tape. This tension must be sufficient to maintain the drive of the clock pulley 100 and to keep the tape inclose contact with the heads such as the trigger head, the high speed head, or the X1 heas as shown in FIG. 2.
In the BF mode a small amount of brake current is allowed to flow through the appropriate motor to maintain the tape tight around all pulleys and especially the clock pulley 100.
The various brake current conditions may be defined as follows:
BA = EA .multidot. Z where Z = State after FF or Fr
BB = EB .multidot. X1
BC = EC .multidot. X30
BD = ED .multidot. X60
BE = EE .multidot. X120
BF = EF .multidot. (FF + FR)
Ea, eb, ec, ed, ee and EF equals voltages applied to the emitter follower Q1 to provide current flow through the motor used for braking.
The schematic shown in FIG. 2A includes the emitter follower Q1 driving either motor M103 or M104 as controlled by the relay K3. A rapid braking of the tape occurs when the Stop control amplifier L10 provides current drive to the emitterfollower Q1 through diodes CR2 and resistor R1. A capacitor C1 delays this current drive to make the braking smooth and to prevent stretching and breaking of the tape. The amplifier L10 also controls a discharge of the capacitor C1 through thetransistor Q2 during any other mode other than the Stop mode so that the Stop mode can be successively repeated. A zenor diode CR3 limits the maximum current during the Stop control.
The brake control logic blocks L11 through L14 are electronic switches which are controlled from the tapedeck speed outputs so as to provide various levels of current to the emitter follower Q1. The reel size switch S1 also controls currentlevel and therefore brake value by switching to a plurality of resistive levels R1, R2 and R3. During the Stop mode or Fast Forward or Fast Reverse modes, the diode CR4 pulls the diode CR1 to a minus voltage such as minus 24 volts and therebydisconnects the speed input and reel size inputs from the emitter follower Q1. During the Play and X1 modes the diode CR4 is back biased to thereby allow the speed input data to go directly to the emitter follower Q1 and control the braking levels ofthe motors M103 and M104.
The tape head and amplifiers shown in FIGS. 2 and 6, provide accurate and stable reproduction of the dual track recorded signals with recorded frequencies from approximately DC to 100 hertz. The basic recording to be reproduced is made from aprior art standard portable recorder operating at approximately 1/8 inch per second or at a reduced speed such as 1/16 inch per second and the recording is directly on the tape without the use of a subcarrier. This type of recording provides forextremely small reels of tape recording for long periods of time, such as 24 hours.
The ECG computer of the present invention provides for analysis of this recorded tape and requires that signals from the recorded tape be played back at real time (X1) or at increased playback speeds of X30, X60 or X120. Since the tape transportsystem allows for the speed of the tape to be switched between any of the four playback speeds, the output signal must have the same equivalent signal bandwidth for all playback speeds.
The output signal must also be stable in gain and base line, and be free from transient switching artifacts.
As indicated above, the recorded signals have a frequency bandwidth of approximately DC to 100 HZ. and the amplifier system must reproduce these signals at any speed. This provides for equivalent frequency bandwidths of DC to 100 HZ. at X1, DCto 3,000 HZ. at X30, DC to 6,000 HZ. at X60, and DC to 12,000 HZ. at X120. Playback heads which will provide the proper reproduction of these signals in real time are shown in application Ser. No. 430,704 and reference is made to this applicationfor details of such a head construction.
FIG. 4 illustrates a miniature recorder which may be used to provide the recorded ECG signals of the type disclosed above. The recorder of FIG. 4 includes several advantages over prior art recorders but it will be appreciated that prior artrecorders may be used to record a tape with ECG signals, and with this tape reproduced by the ECG computer of the present invention. In FIG. 4, the recorder includes an outer case 120 which has a lid 122 to completely enclose the recorder. A pair ofreels 124 and 126 is used to hold the tape during recording. The tape 128 is shown extending from reel 124 to reel 126 and passing over a series of guide members and also over a head member 130 for recording the ECG signals. A capstan drive generallyshown at position 132 is used to move the tape at a constant rate. The portion of the recorder described so far is generally the same as that present in the prior art recorders, but the recorder of the present invention also includes additionalfeatures.
Specifically, the recorder of FIG. 4 includes a display of 134 which provides for a visual output indication of time. The cover 132 includes an opening 136 so that the time is visible through this opening. The signal input from the electrodesattached to the patient is provided to the recorder through a connector which plugs into connector portion 138. A test output 140 may be used in providing for a test of the operation of the recorder.
An event button 142 is used to actuate a burst signal which is supplied to the tape in lieu of one of the tracks of ECG signals upon command by the patient. Specifically, whe the patient experiences a predetermined event, such as an unusualactivity or some sympton which relates to a difficulty in which the patient has been experiencing, the patient is instructed to press the event button, so that the event marker is recorded on the tape. The time display 134 can either be run continuouslyor may be actuated in accordance with the pressing of the event button. In either case, after the patient presses the event button, he may also make a log of the time that the event occurred, plus a description of the event. Upon play back, the eventmark on the tape will be automatically detected during auto-scan so that the tape can be slowed down to real time with a real time write out of the ECG signals corresponding to the event. The ECG signals may now be correlated with the log notation ofthe patient.
FIG. 5 illustrates a block diagram of the event mark pulse generator which is included in the recorder shown in FIG. 4. FIG. 5(a) are waveforms which are used to explain the operation of the block diagram of FIG. 5.
The event mark pulse generator of FIG. 5 is designed to provide a burst of symmetrical square waves of a precision amplitude. For example, the square waves may be at a frequency of 8 HZ. and have an amplitude of 2.0 millivolts peak to peak. The burst produced by the generator provides three basic function. First, the burst is used to automatically mark the tape upon the patient actuating the event mark switch 140 which marking of the tape correlates with either symptoms or activitiesexperienced by the patient. In addition, as indicated above, the patient may keep a log of the time of day at which he activated the event mark switch and may also indicate the nature of the event. Secondly, the burst provides a signal on the tape withcharacteristics sufficiently dissimilar to the ECG signals, so as to be reliably detectible by an electronic detection system in the ECG computer. This detection then provides for the automatic real time write out during the auto-scan cycle. Thirdly,the burst may provide a means for verifying the system calibration throughout the recording period which may be used to assure system accuracy.
The event mark pulse generator of FIG. 5 provides the precise burst of pulses as shown in line E of FIG. 5(a) and specifically, this burst may be a precise 2 millivolt peak to peak 8 HZ., 8 cycle pulse. This type of a pulse will insure reliabledetection in the presence of a wide variety of ECG and artifact characteristics.
The pulse generator specifically consists of a stable, fixed rate clock source 144 which produces an output signal as shown in line A, FIG. 5(a). The clock signal is passed through a gate 146 and clocked into a counter 148 which divides thesignal down. The clock can have any particular frequency and for example, may be at 256 HZ. The counter 148 divides this frequency down to an output of 2.sup.P. The 2.sup.P output is twice the number of pulses desired in the burst and in our specificexample would be a 16 HZ. output. This 16 HZ. output is passed to an electronic double throw single pole switch 150, which is used to interrupt the normal signal path which comes from an amplifier path 152. The normal signal path is from theamplifier 152, through the switch 150, and to a head modulator 154 to drive the recording head.
When the switch 150 is in position to record the burst, an 8 HZ. output is applied through a precision gain scaling network 156 to established burst and amplitude. The switch 140, which may be activated by the patient, is used to initiate apulse through a capacitor 158. Specifically, depressing the switch 140 creates the differentiated pulse as shown in line B of FIG. 5(a) which resets all of the counter inputs to logic zero.
The 2.sup.P output of the counter which is the 16 HZ. output is inverted by invertor 160 to provide an enabling input to the clock input of the counter through the gate 146. The 8 HZ. output or the 2.sup.N output as shown in line D of FIG.5(a) is selected to be the pulse frequency desired. The clock frequency M which as indicated above, may be 256 HZ., is selected as a binary multiple of the desired pulse frequency. When P number of pulses have been generated, the 2.sup.P output returnsto a logic "1" which is a high voltage level, thus disabling the clock input and preventing further pulse generation until the next switch 140 activation.
The counter output (2.sup.P or 16 HZ.) transfers the electronic switch 150 from the normal ECG position, to the burst position during the logic "1", thus preventing interference of burst signal by the ECG signal and improving playback decodingreliability. Specifically, the switch 150 is inserted between the ECG amplifier 152 and the head modulation driver 154 is referenced to the recording circuit ground by a bias resister 162. In addition the gain scale network is used in order to providepulses which are bi-polar and symmetrical with respect to the ECG base line to prevent any DC component from altering the base line after termination of the burst during playback.
Turning now to the reproduction of the ECG information, the output from the real time head 208 is applied to a sensitive amplifier 164, as shown in FIG. 6, and the amplifier is followed by the 66 db integrator 166. The loss from the integrator166 must be made up by the amplifier 164 in order to insure a sufficient output signal from the integrator.
A separate high speed head 204 is used for the reproduction at X30, X60 and X120 playback speeds. This high speed head 204 may be a conventional stereo playback head which has a frequency response of 3 to 12,000 HZ. The frequency responsenecessary for the X30 playback, which is equivalent to 3 and 3/4 inches per second is 3 to 3,000 HZ. The frequency response at the X60 playback, which is equivalent to 71/2 inches per second, is 6 to 6,000 HZ. and the frequency response for the X120playback, which is equivalent to 15 inches per second, is 12 to 12,000 HZ.
The high speed head 204 shown in FIG. 6 supplies its output signals to the high speed amplifier 168 which is a DC amplifier having a response from DC to 15,000 HZ. This amplifier has its gain programmed in accordance with the tape speed signalprovided from the system of FIG. 2. The output from the amplifier 168 is coupled to a programmed integrater 170 which intergrates the output signal to give a flat response from 3 to 12,000 HZ. As shown in FIG. 6, a plurality of switches control theintegrater 170 in accordance with the tape speed and a frequency programmer controls the frequency response of the integrater in accordance with the tape speed. Typically, the amplifier 168 is programmed for gain for the different gain outputs from thehead at the three tape speeds. Frequency programming of the integrater 170 for the three tape speeds in the ratio of 1, 2 and 4 for the speeds of X30, X60 and X120 is accomplished by switching the value of the capacitator CF. The value of theintegrating circuit 170 may also be switched in the ratio of 1, 2 and 4 to control the integrating time constant at the different speeds.
The integraters 166 and 170 are placed at the output of the amplifiers 164 and 168 to insure that all noise picked up from the heads or amplifiers is then attenuated by these integraters. This will give an extremely noise-free output without any60 HZ. interference. The output from the integraters 166 and 170 are connected to high pass filters 172 and 174 so as to remove any DC component which may have been provided by the amplifiers 164 and 168. The output from the high pass filters 172 and174 may then be switched using the switch S2, and the switch S2 may be an FET electronic switch so as to provide a transient free base line to insure that all subsequent components in the system are not disturbed. As indicated above, the switch S2 maybe an electronic FET switch which may be digitally controlled in accordance with the tape speed so as to provide switching between several modes. These modes may be the X1 playback speed mode, the high speed mode, and a switching to ground mode. Forexample, during Fast Forward, Fast Reverse, or Stop, the amplifier output is switched to ground to prevent any transient signals from showing on the output.
As indicated above, and as shown in FIGS. 2 and 6, the tape transport uses two playback heads 204 and 208 to achieve the real time playback at X1 and the high speed playback at X30, X60 and X120 times recorded time. In addition to the use of twoplayback heads to achieve optimum fidelity to the recorded signal for the various playback speeds as explained above, the use of two heads also allows for the viewing of the ECG signals at high speed in a superimposed display on the oscilloscope 10 and asubsequent slowdown to the X1 speed to provide a paper writeout on the paper writer 12 of the same information previously viewed on the oscilloscope. FIG. 7 illustrates the tape loop including an adjustable time delay loop portion to allow for theoperator of the ECG scanner to provide for the proper manual paper writeout in accordance with the previous high speed viewing and in accordance with the reaction time of the operator. The automatic real time paper writeout will be described at a laterportion of the specifications, but the ability to provide the rapid switching between different speeds will be described with reference to the manual actuation by an operator.
The manual paper writeout in real time after viewing at high speed is possible since the direction of tape flow is from right to left. Specifically, the magnetic tape from the supply reel 200 is guided by a plurality of tape guides to pass overa trigger head 202 and the high speed head 204. The tape is then guided by guide members to a variable delay loop portion 206. The tape is then guided by guide members to pass over the X1 head 208 and around the optical encoder pulley 100 to bereceived by the take-up reel 210. The variable delay loop 206 is used to vary the time before the tape is received at the X1 head 208 after being viewed by the high speed 204. The delay loop 206 provides a variation in time from a minimum value inaccordance with the position of the variable delay loop. The delay loop 206 includes a guide roller 212 which can be adjusted along a vertical path in accordance with the movement of the guide roller by a guide arm 214. A clamping knob 216 is used toclamp the arm 214 and roller 212 in the desired position. A pointer member 218 extends from the guide arm to give a visual reading of the delay time.
The adjustment of the position of the guide roller 212 is variable to enable different operators to adjust the quantity of ECG signals that are written out prior to the desired portion and also the compensate for differences in operator reactiontime. For example, the operator may be operating the Electrocardioscanner at X120 playback speed and may be viewing the superimposed image on the oscilloscope. The operator can see a single abnormal ECG beat, such as a PVC, since this will produce acharacteristic visual and audio deviation from the normal superimposed image. Without hesitation, the operator presses the desired auto ECG key to change the speed to real time and to activate the paper writer. Because of the delay loop, the ECGcomplex having the PVC and some previous quantity of ECG complexes will be written out by the paper writer.
Since different operators may desire to view the superimposed image at different ones of the high playback speeds, such as either the X30, X60 or X120 speeds, the time required for the tape to move from the high speed head 204 to the real timehead 208 varies in accordance with the speed of playback. Specifically, the delay time varies from 2 seconds to 0.5 second at the different speeds with the variable guide member 212 adjusted to provide for the minimum delay loop. The delay loop 206when adjusted at its maximum position doubles the times before the tape passes from the high speed head 204 to the real time head 208. It is to be appreciated that when the operator switches from high speed playback to low speed playback, the tapemovement is quickly reduced, so that the actual time before the tape previously viewed at high speed reaches the low speed head 208 is considerably in excess of the time periods given above. For example, if the tape speed could be instantaneouslyreduced to real time after the tape has passed by the high speed head 204, the minimum time the tape would take to get to the real time head 208 would be approximately 60 seconds. The variable delay loop means when adjusted to its maximum positiondoubles the time to 120 seconds. This allows the operator to write out a significant quantity of the ECG complexes prior to the irregularity, so as to help in the analysis of the medical problem. Since the onset of the irregular ECG beat may in itselfcontain valuable information.
The use of the variable delay loop 206 is important since the operator does not have to rewind the tape to write out a complex that he has already reviewed. As indicated above, the delay loop 206 also allows for different operator reaction timesand these times would be different for different operators and would be different for the same operator as his proficiency changes due to training and experience.
The method of scanning at high speed and superimposing ECG complexes on an oscilloscope has been described above with reference to U.S. Pat. Nos. 3,215,136 and 3,718,772 which have issued on the dual track method and the single track method. The superimposed ECG presentation on the oscilloscope may be achieved using a trigger signal from the trigger head 202 which starts the cathode-ray tube trace before the P wave portion of the ECG complex. The position where the waveform starts relativeto the start of the trace is variable to allow viewer preference or to make up for any inaccuracies associated with the trigger system. In addition, since the playback operates at speeds of X30, X60 and X120, the time between the ECG complexes will varywith the playback speed. In order to insure that the complex does not change in shape or duration, the display time base speed varies with the tape speed. The time delay at the beginning of the trace also varies with playback speed to insure that theoverall ECG complex remains superimposed with changes in tape speed. This general system for triggering is described in detail in above-referenced U.S. Pat. No. 3,718,772 and reference is made to this patent for full details. In addition, applicationSer. No. 430,704 describes a specific system which may be used for triggering and response is made to this application for additional details of a triggering system.
The recorder, as shown in FIG. 4, generates a signal burst as shown by the block diagram of FIG. 5 each time the event button 142 is pushed and as indicated above, the signal burst consists of a train of pulses as shown in line D, of FIG. 5(a)over a 1 second period. This signal burst interrupts the ECG being recorded on the recorder on one of the tracks. On playback, the tape may be scanned at X30, X60 or X120 real time and passes the high speed head 204 as shown in FIG. 9.
The output from the head 204 is amplified by amplifier 220 and the signal normally has the appearance of a differentiated signal so that it provides for a pulse at the beginning and end of each one of the square wave components of the burst. This differentiated signal is shown as an input to a comparitor 222 which also includes filtering. The comparitor 222 outputs pulses above a certain level and the output of the comparitor 222 is applied to a counter 224. The comparitor 222 may alsoinclude an inhibit input from a cycle so as to allow for the ECG computer to cycle the trend analysis completely to the end and then reverse this tape to the beginning and the cycle through to detect the events.
The output from the counter is passed through a pulse train interval detector 226 and then through a pulse width detector 228. The pulse train interval detector 226 may be a one shot to insure that the train of pulses occur in 1 second. Thepulse width detector 228 may also be a one shot to determine that the pulses are of the proper width. The counter 224 may be a counter that provides an output when there is a pulse train having pulses between 8 to 11 counts. In this way the codingconsists of counting a pulse train to see if it has between 8 and 11 counts, determining if this pulse train occurs in a time period equivalent to a 1 second train at real time and then determining if the pulse width is equivalent to the recorded pulsewidth. After each of these conditions is determined to be true, then a burst-out signal goes to a delay circuit 230 to start a counting process.
The burst-out signal passes through the switch 92 as shown in FIG. 1(a) to control whether the ECG computer during auto-scan will be responsive to the events which have been marked on the tape by the patient. In addition, the input to the delaycircuit 230 may be from one of a number of inputs shown in FIG. 9 to be controlled by switches 86 through 96 which are generally the switches shown in the computer auto-write section 72 in FIG. 1(a).
The delay circuit 230 counts approximately 96 encoder clock pulses for the switch 76 in the half speed position, or 48 encoder clock pulses for the switch 76 in full speed position, which count indicates that the tape has moved 96/16 inches sincethe tape moves either 1/16 or 1/8 inch for each pulse in accordance with the position of the switch 76. The optical encoder which is disclosed in greater detail in FIG. 2 is coupled to the tape since the encoder is driven by the pulley 100 and the shaft240. The count by the delay circuit 230 starts after a burst has been received or a signal representing an event is coupled through switches 86 through 96 and applied to the count start input of the delay circuit 230.
After a count of 96 or 48 counts, in accordance with the position of the switch 76, the signal that was detected at the high speed head 204 shown in FIG. 2 moves towards the X1 head 208 and is controlled to slow down to real time at a positionapproximately 1 inch from the head gap of the X1 head 208. Specifically, the tape is controlled to slow down from any of the preselected high speeds to the X1 real time speed which is at 1/8 inch per second. This slow down is provided by an output froma timer 232 which puts out an X1 tape speed signal to control the tape deck and override any of the original tape deck's speed control signals. The particular period of time that the tape is written out at the X1 real time speed is determined inaccordance with the position of the switch 84 and may be in a specific example, 15 seconds, 30 seconds or 60 seconds of real time write out.
At the end of the real time write out, a tape deck speed memory 234 is activated by a signal from the timer 232 to return the deck to the original high speed of either X30, X60 or X120. The memory circuit which may be a flip-flop memory latch isactivated from the original tape speed commands to remember at which speed the tape deck was travelling and then to return the tape deck to this speed after the period of real time write out.
If additional real time signal write out is required to the period prior to the event signal, the delay loop shown in FIG. 7 may be extended to write out up to an additional 60 seconds of real time. Normally, the position of the delay loop wouldbe at the minimum position, but this minimum position can be adjusted up to the additional 60 seconds of real time write out.
FIG. 9(a) illustrates the typical write out of real time information during auto-scan with the delay loop in the minimum position, and with approximately an 8 second write out prior to the event, and with an adjustable write out for the totalevent from 15 to 60 seconds. The 1 second burst is shown in the middle, but normally, this is only present in one of the tracks of write out and only if the auto-scan real time write out was activated by the burst signal. If the auto-scan real timewrite out is actuated by the detection of preselected events present in the ECG signals, this burst would not be present.
In order to provide for a digital clock in accordance with the tape travel, a clock drive mechanism as shown in more detail in FIG. 10 is used. In FIG. 2 and in FIG. 7, the clock drive pulley 10 was shown to be part of the tape path and thispulley is maintained in constant engagement with the magnetic tape as provided by the tape tensioning features described above. The pulley 100 provides a drive to an optical encoder which in combination with the pulley provides for the basic clockdrive. Since these mechanical elements are controlled by the movement of the magnetic tape, they are generally designed to be lightweight and to have a relatively low inertia.
A shaft member 240 is coupled from the drive pulley 100, and includes a slotted disc 242 positioned at the end of the shaft, so that the slotted disc 242 moves with movements of the drive pulley 100. The disc may have 48 slots per revolution anda movement of the magnetic tape is translated into a rotation of the disc 242. A pair of light sources 244 and 246 which may be LEDs provided light energy directed towards the disc and specifically to pass through the slots in the disc 242. A pair oflight detectors such as photocells 248 and 250 detect light output from the light sources 244 and 246. The diameter of the pulley 100 is adjusted so that each 1/16 inch of tape travel causes a signal output from each of the photocells 248 and 250. Inaddition, the photocells are spaced apart so that one photocell produces an output signal 90.degree. in phase ahead of the other so as to indicate the direction of tape travel. This can be shown in FIG. 10(a) where the output of photocell 248 is shownin solid line and the output of photocell 250 is shown in dotted line.
The output signals from the photocells 248 and 250 are applied to amplifiers 252 and 254, which may be conventional buffer gates, so as to provide for amplified square wave pulses to be directed to a time clock. Since an output signal for each1/16 inch of travel is provided at real time playback, an output signal each second is provided to the digital clock. Referring now to FIG. 11 the output of the optical encoder and input to the digital clock is shown to be square wave pulses having a90.degree. shift.
The digital clock system, shown in FIG. 11, provides a visual output clock as shown at position 16 in FIG. 1. In addition, the digital clock provides output information which is used in the paper writer section by printer mechanism 14 to providefor printout of the digital clock information. As indicated above, the optical encoder measures tape length in 1/16 inch units and the digital clock system converts this to changes in time of day either increasing or decreasing. This is accomplished atthe various playback speeds in addition to the fast forward and fast reverse speeds. A plurality of preset inputs 256, 258, and 260 allow the presetting of each digit to any number so that the start time of the digital clock can be correlated to thestart time of the recording which is to be analyzed.
The digital time clock keeps track of the recorded time on a 12 hour basis and provides visual time of day outputs as shown by indicators 262 through 268. In addition, a pair of output indicators 270 and 272 provide a visual indication of AM orPM so as to cover a full 24-hour day.
The digital clock is operated in a bidirectional mole either counting up or down and controlled by an up-down logic gate 274 and with each input pulse proportional to one second. Logic gate 274 determines which signal A or B comes first and thenactuates standard up-down counters to count in the proper direction. The digital clock also provides output BCD signals of each digit in sequence which relate to the visual indication and to the AM-PM. These output command signals may either becontrolled from internal timing controls such as an event or a marker control, or from an external input. For example, at a particular event or at a particular preselected time, a printout of the time may be provided by the printer 14 on the paper. This printout would be a typical digital printout such as 11:59 AM.
In addition to the printout of time, the digital clock provides additional sequential information to be printed immediately after the printout of the time. For example, the arrhythmia computer provides digital information as to the number of VEsand SVEs and in addition to the printout of time, the number of such VEs and SVEs may be printed out. This typically occurs when the tape transport and display operates in the trend mode. The typical printout is as follows: 12:00 AM 032 060. Theprinting of the numerals after 12:00 AM occurs sequentially, one at a time, after the AM has been printed.
The three numbers represented by 032 indicate the number of VE beats and the three numbers represented by 060 indicate the number of SVE beats. Both of these numbers are provided from the arrhythmia computer portion of the system and the time ofprinting is controlled by the digital clock.
As indicated above, the digital clock controls a printout by the paper writer of the time when operated in a trend mode. At that time, the paper is moved at a relatively slow speed. The paper writer may be of that heat stylus type and would usea heat stylus located in the upper portion of the paper writer 12 and as represented by heat styli 276 and 278 as shown in FIG. 1. The digital printer 14, shown in FIG. 1, has a mechanical separation from the heat styli 276 and 278 and because of thismechanical separation, the visual printout would normally have time errors.
Specifically, since the digital printer is ahead of the writing styli, the writing styli provides the writing of information correlating to a particular time on the recorded tape and the digital printer is considerably ahead of the writing styli. At low paper speeds, such as in the trend mode, the time error is considerable. As an example, the separation between a print wheel, which is part of the digital printer 14, and the writing styli 276 and 278 may be on the order of 8 centimeters. At apaper speed of 1 millimeter per second, this would represent a time error of 80 minutes. The digital clock shown in FIG. 11 corrects for this time error for paper speeds of 1 millimeter per second or 2 millimeters per second, which correspond to thetape playback speeds of X60 or X120. Generally the tape playback speeds of X60 or X120 are the only ones used in the trend mode. Specifically, the correction for the time error is generated from the signals which are used to provide for the digitaldisplay.
During a trend printout, the time is digitally printed with this time correction of 80 minutes. When the data written by the styli 276 and 278 gets to the area of the printer 14, the correct time is then printed along the edge of the paper. Themethod of achieving this printout is greatly simplified in that only one set of components is used to drive the digital display and then this same BCD data as displayed is modified to provide a correct printout of the time.
As shown in FIG. 11, the up-down control 274 is driven by the output pulses from the optical encoder which corresond to a one-second rate for each 1/8 inch of tape. Depending on the direction of tape travel, one of the pulses always leads theother, so as to provide for the up-down control producing the appropriate output pulses to drive the dividers 280 through 286 and the drive 288, which controls the AM-PM indication.
The display indicators 262 through 272 may be standard LED or Nixie tubes and displays four numbers such as 11:59 to indicate the time and also the AM-PM indication. Since the output of the up-down control 274 corresponds to a one-second rate,the first divider 280 divides by 60 to change the one-second rate to minutes and to drive first display 268. The succeeding logic dividers 282, 284 and 286, convert the minutes to tens of minutes by dividing by ten, to hours by dividing by six and totens of hours by dividing by 10. Finally, the divider logic 288 provides an output indication of AM or PM at 12 o'clock.
The first three least significant digits may be changed any time by controls 256, 258 and 260, so as to initially set the indicators and dividers to a desired time which corresponds to the start time of recording on the recorded tape. The mostsignificant digit is controlled by the set switch 256, so that this set switch not only sets its own indicators 264, but at the change from 9 to 0, the most significant digit is changed from 0 to 1, and when the displays 264 and 262 go from 11 to 12, theAM-PM lamps are also activated.
During the X1 playback mode, the digital time is normally printed on the paper writer by the unit 14 from either an external push button command or at the actual start of the paper writer. These two inputs are shown provided to the data selectormultiplexer 290 which includes counters and gates to look at each BCD number in sequence, one at a time. In the X1 playback mode, the actual time of day from the clock output drivers 280 through 286 are connected to a latch multiplexer 292 via theprinter trend mode correction unit 294. The latch 292 is formed of flip-flops to hold the digital value of the display in BCD form. The unit 294 is formed from gates which are sampled by the clock 296 and then outputted into the latch 294. The paperspeed from the trend or X1 signals is inputted to control the take off point, with the correction of 80 minutes when desired. The printer trend mode correction is controlled during the X1 playback mode to merely pass on the clock outputs to the latchmultiplexer 292. The data from the latch 292 and multiplexer 290 is multiplexed out in sequence at a rate determined by the data sequence clock 296. The clock 296 is of standard design having an output pulse rate controlled by the speed of the paperwriter so as to output the printer at a slow rate on trend or at the faster rates of 25 or 50 mm/s on X1.
In the X1 operate mode, the paper writer is driven at a relatively high speed and the time differential between the writing of the data by the heat styli 276 and 278 and the time printout by the unit 14 is relatively small. This time error is onthe order of 4 to 5 seconds and no time correction may be necessary in this mode. It is to be appreciated, however, if such a time correction is desired, it could be provided by conventional means by using a time delay in the printout of theinformation. The output from the multiplexer 290 is BCD data, and this data is coupled through a BCD interface 298 to the external digital printer 14, where generally one digit at at time is printed. The print commands to the printer 14, whichcorrelate to the BCD data, is supplied by the data sequence clock 296. In addition, print inhibit signals are supplied to and from the data sequence clock. During the X1 playback mode the data dequence clock is reset to start over, after the AM or PMis printed.
With the exception of the time of printing by the digital printer 14, the digital time clock operates the same as the X1 speed and at faster tape transport speeds. During X60 or X120 trend, analysis of the ECG complexes is provided and outputsignals reflecting this analysis as a trend is written by the paper writer. This output trend data consists of analog heart rate, analog ST level, event marks and the digital printout of time and number of VEs and SVEs, both of which are determined bythe arrhythmia computer. As described above, a time correction must be made during the trend mode to correct for the mechanical spacing between the heat stylus and the digital printer. Specifically, the time that is printed by the digital printer 14during the trend writeouts is corrected by 1 hour and twenty minutes. This enables the heat stylus writeout to proceed to provide writeout with the paper moving at a slow rate and with the correct time printed along the paper edge.
In order to provide this time correction of one hour and twenty minutes, the printer trend mode correction unit 294 provides the following operation. The input data proceeds into the unit 294 until the two least significant bits reach 59. After59 is changed to 00 in unit 294, but before the next hour digit is changed, the clock data from the unit 294 is sequenced at a high rate into the latch 292 and is then inhibited from further change for an hour. The latch 292 therefore receives the timeas 11:00 AM, rather than 12:00 as displayed by the display elements 262 through 268. A twenty minute delay in printing is then initiated by waiting until a 2 occurs in the second least significant digit, such as at 12:00 AM on the digital display,before the printer 14 is commanded tp printout the information held in the latch 292 which would be 11:00 AM. The printing of the time is then followed by an event mark as shown in FIG. 12.
After the event mark, the arrhythmia computer output would supply information to be printed at positions following the time as explained above. The output circuitry of the arrhythmia computer is connected in parallel with the digital time clockto supply information to the digital printer. The data sequence clock 296 is used to control the sequential printing from the arrhythmia computer of the information supplied by the arrhythmia computer.
In FIG. 13, is shown a typical auto-scan chart write out, including trend information which would be identical to that shown in FIG. 12, but additionally including periodic write out of real time information in response to inputs from the burstdetector, arrhythmia computer, ST computer or heart rate computer. Normally, during the auto-scan cycle, the trend data of heart rate and ST level is written out in a normal way as shown in FIG. 12. ECG write out at the real time speed during this timeis inhibited. At the end of the tape an automatic reversal is initiated to the beginning of the tape and after a slight delay, the tape then scans at the original fast speed.
The initial write out is shown in the left-hand portion of FIG. 13, identified as portion 300 and is indicated to be Trend Cycle 1. During the second cycle, inputs from the burst detector, arrhythmia computer, ST computer or heart rate computermay activate the real time write out mode for a predetermined time of 15, 30 or 60 seconds. For example, portion 302 of FIG. 13 shows one real time ECG data write out and identified as ECG Data Cycle 2. Following this typical real time write out, thetrend data is again plotted to show the heart rate and ST level in the normal fashion, and this is shown at 304 of FIG. 13 and is identified as Trend Cycle 2. If the event burst is again detected, or if one of the other external inputs from thearrhythmia computer, ST computer or heart rate computer is detected, the system will again write out real time ECG data. This is shown at portion 306 of FIG. 13 and identified as ECG Data Cycle 2 and would have the same period as the previous real timewrite out. During the write out at real time, the time of such write out relative to the time at which the recording was made, may be printed to show the time of the unusual activity. The process of writing out the trend information with periodic writeout of real time ECG information, in accordance with the detection of an unusual occurrence, may be repeated many times during the auto-scan write | | | |
