CARDIAC ARRYTHMIA DETECTOR

• US 3,759,248 A
• Filed: 02/08/1971
• Issued: 09/18/1973
• Est. Priority Date: 02/08/1971
• Status: Expired due to Term

• Current Assignee: Donley J. Valiquette
• Original Assignee: Donley J. Valiquette
• Inventors: Valiquette, Donley J.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US05/113,331
• Time in Patent Office: 953 Days
• Field of Search: 128/2.6A,2.6F,2.6R,2.5R
• US Class Current: 600/516
• CPC Class Codes: A61B 5/336 Magnetic recording apparatus
• CPC Class Codes: A61B 5/35 by template matching
• CPC Class Codes: A61B 5/364 Detecting abnormal ECG interval, e.g. extrasystoles, ectopic heartbeats

Abstract

A system is described to continuously monitor a number of cardiac patients in a hospital. Electrocardiogram probes are placed upon a plurality of patients and simultaneously monitored by this system for changes in the normal electrocardiogram (ECG) waveforms. Each ECG waveform is recorded on a 30 second tape loop delay for retrieval during an alarm condition for a determination of the cause of the alarm. This tape loop also provides a 100 millisecond delay of ECG for correlation monitoring of the QRS complex of the ECG. An R wave trigger is generated and is utilized for R-R interval measurements. A correlation monitor is provided and quantizes the ECG QRS complexes and stores each segment thereof for comparison with subsequent waveforms. The stored waveform provides a running average of several QRS complexes just prior to the complex being compared. A segment element is trained by this running average of the QRS waveform. By comparing each segment of the waveform to the appropriate segment of the stored waveform, a correlation is established. If an aberrant QRS complex is sensed and compared, several points of difference will be detected. The R-R interval is simultaneously compared on a running average to assist in establishing a premature ventricular contraction of the patient. A photoplethysmograph is provided to monitor mechanical heart action. The signals provided by the R-R interval monitor, a change in the QRS complex, pulse signals provided by the photoplethysmograph and the heart rate of the patient provide certain criteria which are monitored by a logic circuit to provide a minor alarm on certain criteria and a major alarm on any combination of the waveforms.

Claims

1. A system for accumulating aberrant beat values of a cardiac patient comprising:

first means for detecting spatial changes in a train of electrocardiogram waveforms and for providing an output pulse when a spatial change is detected;

a plurality of serially coupled shift registers, the first shift register of said plurality being coupled to said first means, each shift register of said plurality having an output circuit;

an accumulator coupled to each output circuit of each shift register of said plurality to accumulate and store the contents thereof; and

second means coupled to each shift register of said plurality to serially shift a new pulse into the first shift register of said plurality and for serially shifting the contents of each shift register of said plurality at predetermined intervals.

2. The system as defined in claim 2 and further comprising:

a digital to analog converter responsive to the accumulated contents of said accumulator; and

a threshold detector responsive to said digital to analog converter and including a threshold input source, said threshold detector being to provide an output signal wheN the analog valve of the accumulator contents exceed the threshold input.

3. A system for monitoring the cardiac condition of a patient, comprising:

a monitor, responsive to the cardiac condition of the patient and including means for providing ECG signals;

detector means for processing said ECG signals to provide trigger pulses synchronized to a predetermined portion of said ECG signals;

means for storing said ECG signals for a predetermined fixed time interval and for providing delayed ECG signals;

quantizing means synchronized by said trigger pulses for quantizing the QRS complex portion of said ECG signals, and for providing quantized QRS signals indicative of the value of the respective quantized segments;

filter means coupled to said quantizing means for forming the time weighted average value of the quantized QRS signals for the respective segments;

comparison means for comparing said quantized QRS signals to their respective time weighted average value, and for providing a pattern change signal if differences therebetween exceed a preselected value; and

alarm means responsive to said pattern change signal, for providing an alarm signal.

4. The system of claim 3 further comprising:

temporary storage means for storing the ECG signals for a second predetermined interval; and

permanent storage means coupled to said temporary storage means and enabled by said alarm signal, for permanently recording said ECG signals;

whereby said permanent storage means records ECG signals which occurred during said second predetermined interval prior to said alarm signal.

5. The system of claim 3 wherein:

said detector means includes peak detector means for providing said trigger pulses in synchronization with the peak level of each QRS complex.

6. The system of claim 5 wherein said peak detector means comprises:

a low pass filter buffer amplifier responsive to the ECG signals from said monitor;

a first bandpass filter coupled to said low pass filter;

a biphasic amplifier coupled to said first bandpass filter and adapted to invert negative portions of the QRS complex to provide positive output signals therefrom;

an automatic gain control amplifier responsive to the output signals from said biphasic amplifier;

a second bandpass filter responsive to the output signals from said automatic gain control amplifier;

a peak transition detector responsive to the peak of the output signals from said second bandpass filter; and

pulse forming means for providing said trigger pulses in response to the output signals from said peak transition detector.

7. The system of claim 3 wherein:

said comparison means includes means for forming difference signals indicative of the difference between respective ones of said quantized QRS signals and their time weighted average values; and

means for combining said difference signals to form a composite difference signal; and

means for producing said pattern change signal when said composite difference signal exceeds a preselected value.

8. The system of claim 3 further comprising:

means for determining the interval between said trigger pulses and for providing an R-R interval signal indicative thereof;

means for forming the time weighted average value of said R-R interval signals and for providing an average R-R interval signal indicative thereof; and

means for comparing said R-R interval signal against said average R-R interval signal, and for providing an R-R interval change signal when the difference therebetween exceeds a preselected value.

9. The system of claim 8 wherein:

said detector means includes peak detector means for providing said trigger pulses in synchronization with the peak level of each QRS complex, and said peak detector means comprises;

a low pass filter buffer amplifier responsive to the ECG signals from said monitor;

a first bandpass filter coupleD to said low pass filter;

a biphasic amplifier coupled to said first bandpass filter and adapted to invert negative portions of the QRS complex to provide positive output signals therefrom;

an automatic gain control amplifier responsive to the output signals from said biphasic amplifier;

a second bandpass filter responsive to the output signals from said automatic gain control amplifier;

a peak transition detector responsive to the peak of the output signals from said second bandpass filter; and

pulse forming means for providing said trigger pulses in response to the output signals from said peak transition detector.

10. The system of claim 8 further comprising:

means for producing an alarm signal upon the occurrence of a pattern change signal and an R-R interval change signal.

11. The system of claim 10 further comprising:

temporary storage means for storing the ECG signals for a second predetermined interval; and

recording means coupled to said temporary storage means and enabled by said alarm signal for recording said ECG signal;

whereby ECG signals which occur during said second predetermined interval preceding said alarm signal are recorded.

12. The system of claim 8 wherein:

said monitor means further includes means for providing a signal indicative of the heart rate of the patient; and

said system further comprises means for providing a heart rate alert signal when said heart rate signal is outside of a preselected range, and means for producing an alarm signal in response to a predetermined combination of said pattern change, R-R interval change and heart rate alert signals.

13. The system of claim 8 wherein:

said monitor means further comprises means for providing a signal indicative of the heartrate of the patient; and

said system further includes means for providing a heart rate alert signal when said heart rate signal is outside of a preselected range;

means for detecting a low pulse level and for providing a pulse level alert signal indicative thereof; and

means for producing an alarm signal in response to a predetermined combination of said pattern change, R-R interval change, heart rate alert and pulse level alert signals.

14. The system of claim 13 further comprising:

means for producing a minor alarm signal upon the occurrence of any one of said pattern change, R-R interval change, heart rate alert and pulse level alert signals; and

means for providing a major alarm signal upon the occurrence of any two of said pattern change, R-R interval change and heart rate alert signals.

15. A system for monitoring the cardiac condition of a patient in response to ECG signals applied thereto, said system comprising:

detector means for processing said ECG signals to provide a trigger pulse in synchronization with a predetermined portion of each ECG signals;

means for storing said ECG signals for a predetermined time interval and for providing delayed ECG signals;

means synchronized by said trigger pulses, for quantizing said delayed ECG signals and for providing pattern segment signals indicative of the pattern of each ECG signal;

means for forming the time weighted average of corresponding pattern segment signals;

means for producing a pattern change signal as a function of the difference between said segment signals and the corresponding time weighted average value thereof; and

alarm means, responsive to said pattern change signal, for providing an alarm signal.

16. The system of claim 15 wherein:

said means for producing a pattern change signal includes means for forming difference signals indicative of the difference between respective ones of said pattern segment signals and their corresponding time weighted average value; and

means for combining said difference signals to form a composite difference signal and means for producing said pattern change signal when said composite difference signal exceeds a preselected value.

17. The system of claim 15 wherein:

said detector means includes peak detector means for providing said trigger pulses in synchronization with the peak level of each QRS complex of each ECG signal.

18. The system of claim 17 wherein said peak detector means comprises:

a low pass filter buffer amplifier responsive to the ECG signals from said monitor;

a first bandpass filter coupled to said low pass filter;

a biphasic amplifier coupled to said first bandpass filter and adapted to invert negative portions of the QRS complex to provide positive output signals therefrom;

an automatic gain control amplifier responsive to the output signals from said biphasic amplifier;

a second bandpass filter responsive to the output signals from said automatic gain control amplifier;

a peak transition detector responsive to the peak of the output signals from said second bandpass filter; and

pulse forming means for providing said trigger pulses in response to the output signals from said peak transition detector.

19. The system of claim 15 further comprising:

temporary storage means for storing the ECG signals for a second predetermined interval; and

permanent storage means coupled to said temporary storage means and enabled by said alarm signal, for permanently recording said ECG signals;

whereby said permanent storage means records ECG signals which occurred during said second predetermined interval prior to said alarm signal.

20. THe system of claim 15 further comprising:

means for determining the interval between said trigger pulses and for providing an R-R interval signal indicative thereof;

means for accumulating the time weighted average value of said R-R interval signals and for providing an average R-R interval signal indicative thereof; and

means for comparing said R-R interval signal against said average R-R interval signal, and for providing an R-R interval change signal when the difference therebetween exceeds a preselected value.