Pacemaker monitoring recorder and malfunction analyzer

• US 4,532,934 A
• Filed: 05/17/1983
• Issued: 08/06/1985
• Est. Priority Date: 11/01/1978
• Status: Expired due to Term

• Current Assignee: DEL Mar Medical Systems, LLC (Bio-Techne Corporation)
• Original Assignee: Del Mar Avionics
• Inventors: Kelen, George J.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US06/495,154
• Time in Patent Office: 812 Days
• Field of Search: 128/697, 128/710, 128/711, 128/419 PT
• US Class Current: 600/510
• CPC Class Codes: A61B 5/337 Playback at speeds other than the recording speed
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61N 1/37 Monitoring; Protecting
• CPC Class Codes: A61N 1/3718 Monitoring of or protection against external electromagnetic fields or currents

Abstract

A system for ambulatory monitoring and subsequent analysis and evaluation of pacemaker performance includes a recorder module which detects pacemaker spikes and in response to each spike generates a signal having a waveform compatible with commericially-available ambulatory ECG recorders, to permit ECG signals to be recorded in one channel of the recorder while simultaneously the pacemaker spike signals are recorded in another channel. The magnetic tape on which the signals are recorded is played back at 120 times the recording speed, typically, on a commercially-available playback analyzer which presents the pacemaker and ECG signals as separate outputs. The system further includes an analysis module connected to the playback unit and receiving from it the ECG signals and the pacemaker spike signals. The analysis module has counters which accumulate the number of paced beats and of fusion beats. The analysis module also includes circuits for sensing manifestations of pacemaker malfunction. When malfunction is sensed, the analysis module reduces the playback speed to facilitate study by an operator and activates a visual alarm. The conditions sensed include: failure-to-sense, failure-to-capture, and abnormal bradycardia.

Claims

1. In a magnetic tape recording system including separate tracks for ambulatory monitoring of the operation of a pacemaker and of the response of a patient to the pacemaker as revealed by the timing relationship between a pacemaker spike signal generated by the pacemaker and an ECG signal generated by the patient equipped with the pacemaker, an apparatus comprising:

first means for in an ambulatory mode for sensing the occurrence of a pacemaker spike signal and ECG signal;

second means for producing in response thereto a pacer tag signal whose frequency spectrum lies within a predetermined frequency bandwidth;

third means for recording the pacer tag signal and ECG signal on separate tracks on said magnetic tape, said fourth means characterized by said predetermined bandwidth, only signals having a frequency within said predetermined bandwidth being recorded on said separate tracks said first, second and third means being ambulatory;

fourth means for stationary operation for playing back the recorded magnetic tape recorded by said third means at a selected one of a plurality of speeds higher than the recording speed at which it was originally recorded;

fifth means for determining during the high speed playback a logical timing relationship between the ECG signal and the pacer tab signal;

sixth means for selecting on the basis of the logical timing relationship of the ECG signal to the pacer tag signal one of several different output signals indicative of the operation of the pacemaker and of the response of the patient to the pacemaker

wherein said fourth means further comprises;

a pacemaker channel;

a separate identical ECG signal channel; and

an analysis module receiving occasional pacemaker spikes in said pacemaker signal channel and receiving occasional QRS complexes in said ECG signal channel, the signals in the two channels being correlated in time by said analysis module, said analysis module producing signals indicative of the operation of the pacemaker, said analysis module including a conditional logic circuit for generating an abnormal bradycardia signal after the occurrence of a QRS complex in the ECG signal channel contingent on the failure of receipt of a signal in said ECG channel within a variable time interval T5 after receipt of a signal in said pacemaker channel, said variable time interval T5 being dependent on playback speed of said fifth means, said signal being indicative of a subsequent QRS complex in the ECG signal channel,

whereby proper operation of said pacemaker in response to heart activity is monitored and verified.

2. The apparatus of claim 1 wherein said second means further comprises:

control means connected to said conditional logic circuit to receive the abnormal bradycardia signal and in response to the abnormal bradycardia signal to generate a command signal for reducing the playback speed.

3. The apparatus of claim 1 further comprising:

setting means connected to said conditional logic circuit for establishing under control of an operator the duration of said predetermined time interval T₅.

4. A system for playing back and analyzing magnetic tapes on which ECG signals and pacemaker spike signals have been recorded simultaneously for the purpose of monitoring the performance of a pacemaker, in which system the tape is played back at a speed higher than that at which it was recorded until the system recognizes from the played-back signals a manifestation of pacemaker malfunction to generate a command signal in response to which the system reduces the playback speed to facilitate interpretation of the signals by an operator and to facilitate production of a graphic record of the signals, said system comprising in combination:

an ECG signal channel;

a separate identical pacemaker signal channel;

playback means for producing electrical reproduction of the signals stored on the magnetic tape at a playback speed greatly in excess of the speed at which the signals were recorded, for presenting the reproduced signals in said ECG signal channel and in said pacemaker signal channel, and for producing signals at a reduced playback speed in response to said command signal;

a conditional logic circuit for generating an abnormal bradycardia signal after the occurrence of a QRS complex in the ECG channel unless said conditional logic circuit detects the occurrence of another QRS complex in the ECG signal channel prior to the end of an event window of duration T5 alterable according to playback speed said conditional logic circuit for establishing said window and for altering said duration T5 according to playback speed; and

control means connected to said conditional logic circuit to receive the abnormal bradycardia signal and in response to the abnormal bradycardia signal to generate a command signal and to apply the command signal to said playback means to reduce the playback speed.

5. A monitoring system for a cardiac patient utilizing a device of the type which generates a prompting signal for initiating a heartbeat comprising:

ambulatory recording means for sensing and recording both ECG and prompting signals, and

wherein said recording means includes;

synthesizing means responsive to sensed prompting signals for producing in response thereto a synthesized signal having a frequency spectrum within the frequency spectrum of ECG signals, and

means for recording said synthesized signal

stationary playback means for measuring the time displacement between prompting signals which occur prior to an ECG complex initiated by the prompting signal, and for measuring the time relationship between the occurrence of ECG complexes and subsequent prompting signals as recorded by said means.

6. The apparatus recited in claim 5 wherein said stationary playback means comprises:

means for playing back recordings made by said recording means at least at one speed different than the speed at which the recording was made and, for identfying the salient synthesized signals based upon their time displacement relative to the occurrence of an associated ECG complex.

7. An apparatus for use with a magnetic tape recorder having at least one channel capable of recording ECG waveshapes and having at least a pair of ECG electrodes connected to the patient for receiving pacemaker spike signals and for receiving an ECG signal, said apparatus comprising:

first means for sensing the occurrence of said pacemaker spike signals, said pacemaker spike signal having a frequency spectrum higher than the highest frequency within the spectrum of said ECG signal;

second means for producing in response to said pacemaker pike signal a synthesized signal whose frequency spectrum lies within the frequency spectrum of said ECG signal; and

third means for coupling said synthesized signal to at least one channel of said magnetic tape recorder,

whereby said recorder will record the waveshape of said ECG as well as the time displacement of the pacemaker signal.

8. An apparatus for use with a magnetic tape recorder having at least two identical channels none of which is capable of recording pacemaker spike signals and having at least a pair of ECG electrodes connected to the patient for receiving pacemaker spike signals and for receiving an ECG signal, said apparatus comprising:

first means for sensing the occurrence of said pacemaker spike signals, said pacemaker spike signals having a frequency spectrum higher than the highest frequency within the spectrum of said ECG signal;

second means for producing in response to said pacemaker pike signals a synthesized signal whose frequency spectrum lies within the frequency spectrum of said ECG signal; and

third means for coupling said synthesized signal to at least one of said channels of said magnetic tape recorder;

whereby said recorder will record the waveshape of said ECG as well as the time displacement of the pacemaker signal.

9. An apparatus for use with a magnetic tape recorder having two identical channels capable only of recording signals in the frequency spectrum of ECG waveshapes and having at least a pair of ECG electrodes connected to the patient for receiving pacemaker spike signals and for receiving an ECG signal, said apparatus comprising:

first means for sensing the occurrence of said pacemaker spike signals, said pacemaker spike signal having a frequency spectrum higher than the highest frequency within the spectrum of said ECG signal;

second means for producing in response to said pacemaker pike signal a synthesized signal whose frequency spectrum lies within the frequency spectrum of said ECG signal; and

third means for coupling said synthesized signal to at least one channel of said magnetic tape recorder;

whereby said recorder will record the waveshape of said ECG as well as the time displacement of the pacemaker signal.

10. An apparatus for use with a magnetic tape recorder having two identical channels capable only of recording signals in the frequency spectrum of ECG waveshapes and having at least a pair of ECG electrodes connected to the patient for receiving pacemaker spike signals, said pacemaker spike signals being outside said frequency spectrum of said ECG waveshapes, and said electrodes for receiving an ECG signal, said apparatus comprising:

first means for sensing the occurrence of said pacemaker spike signals, said pacemaker spike signal having a frequency spectrum higher than the highest frequency within the spectrum of said ECG signal;

second means for producing in response to said pacemaker pike signal a synthesized signal whose frequency spectrum lies within the frequency spectrum of said ECG signal;

third means for coupling said synthesized signal to at least one channel of said magnetic tape recorder; and

fourth means for coupling said ECG signal to said other one of said at least two channels of said magnetic tape recorder,

whereby said recorder will record the waveshape of said ECG as well as the time displacement of the pacemaker signal.

11. In a magnetic tape recording system including separate tracks for ambulatory monitoring of the operation of a pacemaker and of the response of a patient to the pacemaker as revealed by the timing relationship between a pacemaker spike signal generated by the pacemaker and an ECG signal generated by the patient equipped with the pacemaker, an apparatus comprising:

first means for recording on a magnetic tape in an ambulatory mode the occurrence of a pacemaker spike signal and ECG signal, said pacemaker spike signal having a higher frequency spectrum than the highest frequency spectrum than the highest frequency lying within the frequency of said ECG signal;

second means for sensing the occurrence of a pacemaker spike signal and ECG signal;

third means for producing in response thereto a pacer tag signal whose frequency spectrum lies within a predetermined frequency bandwidth, said predetermined bandwidth including the frequency spectrum of said ECG signal;

fourth means including separate recording channels, said fourth means for recording the pacer tag signal and ECG signal on said separate recording channels and separate tracks on said magnetic tape, said fourth means characterized by said predetermined bandwidth, only signals having a frequency within said predetermined bandwidth being recorded on said separate tracks;

fifth means for stationary operation for playing back the recorded magnetic tape at a selected one of a plurality of speeds higher than the recording speed at which it was originally recorded;

sixth means for determining during the high speed playback a timing relationship between the ECG signal and the pacer tag signal;

seventh means for selecting on the basis of the timing relationship of the ECG signal to the pacer tag signal one of several different output signals indicative of the operation of the pacemaker and of the response of the patient to the pacemaker

wherein said fifth means further comprises;

a pacemaker channel;

an ECG signal channel;

an analysis module receiving occasional pacemaker spikes in said pacemaker signal channel and receiving occasional QRS complexes in said ECG signal channel, the signals on the two channels being correlated in time, by said analysis module, said analysis module producing signals indicative of the operation of the pacemaker, said analysis module including a conditional logic circuit for generating an abnormal bradycardia signal after the occurrence of a QRS complex in the ECG signal channel contingent on the failure of receipt of a signal in said ECG channel within variable time interval T5 after receipt of a signal in said pacemaker channel, said variable time interval T5 being dependent on playback speed of said fifth means, said signal being indicative of a subsequent QRS complex in the ECG signal channel,

whereby proper operation of said pacemaker in response to heart activity is monitored and verified.

12. An apparatus for use with a magnetic tape recorder having two identical channels for recording signals indicative of the operation of a pacemaker and the response of a patient to a pacemaker, at least a pair of ECG electrodes connected to the patient for receiving pacemaker spike signals and for receiving an ECG signal, said apparatus comprising:

first means for sensing the occurrence of said pacemaker spike signal, said pacemaker spike signal having a frequency spectrum higher than the highest frequency within the spectrum of said ECG signal;

second means for producing in response to said pacemaker spike signal a synthesized signal whose frequency spectrum lies within the frequency spectrum of said ECG signal;

third means for coupling said synthesized signal to one channel of said magnetic tape recorder; and

fourth means for coupling said ECG signal to said other identical one of said channels of said magnetic tape recorder.

13. The apparatus of claim 12 wherein said first means comprises a differentiator circuit connected to said ECG electrodes to receive an input signal, said input signal couled to said differentiator circuit through said ECG electrodes to produce a differentiator output signal related to the rate of change of said input signal.

14. The apparatus of claim 13 where said second means comprises a synthesized signal generator connected to said differentiator circuit to receive said differentiator output signal and to generate said synthesized signal when the magnitude of said differentiator output signal exceeds a preset threshold level, said synthesized signal having a predetermined waveform recordable by said magnetic tape recorder.

15. The apparatus of claim 14 wherein said synthesized signal has a pulsewidth longer than ten milliseconds.

16. The apparatus of claim 15 wherein said synthesized signal generator is a one-shot multivibrator.

17. The apparatus of claim 14 wherein said synthesized signal has an amplitude greater than 0.5 millivolts.