Apparatus and method for measuring cardiac vagal tone
First Claim
1. An apparatus for providing a measure of vagal tone in a human or animal patient and comprising:
- input means for receiving an ECG signal obtained from a patient;
detection means coupled to said input means for detecting QRS waveforms in said ECG signal and for generating timing data indicative of periods between consecutively received QRS waveforms;
frequency demodulation means coupled to said detection means for demodulating said timing data in real time and for generating a signal corresponding to a frequency modulating signal in said ECG signal, wherein said generated signal is used to provide said measure of vagal tone; and
signal processing means for converting the frequency modulating signal into a linear vagal scale (LVS).
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Abstract
Apparatus for measuring a vagal tone has a detector that detects a QRS waveform of an ECG signal and generates a pulse signal that is integrated by an integrator. The integrator output is passed, in parallel, to a high pass filter and a low pass filter. The filter outputs are passed to respective voltage controlled oscillators (VCOs). The outputs of the VCOs are combined in a phase comparator that generates an output pulse train with the pulse period being proportional to the phase differences of the input signals. The phase comparator output signal is integrated and combined with a DC signal to remove any offset for constant heart rate. The combined signal is applied to a vagal tone gauge, which connects the output into a standard linear vagal tone scale.
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Citations
16 Claims
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1. An apparatus for providing a measure of vagal tone in a human or animal patient and comprising:
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input means for receiving an ECG signal obtained from a patient;
detection means coupled to said input means for detecting QRS waveforms in said ECG signal and for generating timing data indicative of periods between consecutively received QRS waveforms;
frequency demodulation means coupled to said detection means for demodulating said timing data in real time and for generating a signal corresponding to a frequency modulating signal in said ECG signal, wherein said generated signal is used to provide said measure of vagal tone; and
signal processing means for converting the frequency modulating signal into a linear vagal scale (LVS). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for providing a measure of vagal tone from an ECG recorded from a human or animal patient, the method comprising the steps of:
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detecting the occurrence of QRS waveforms in the ECG signal;
generating a timing signal indicative of a time period between consecutively received QRS waveforms;
frequency demodulating said timing signal in real time to obtain a frequency modulation signal, wherein said frequency modulation signal is used to provide said measure of vagal tone; and
converting the frequency modulating signal into a linear vagal scale (LVS) using a signal processing means. - View Dependent Claims (13, 14)
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15. An apparatus for providing a measure of vagal tone in a human or animal patient and comprising:
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input means for receiving an ECG signal obtained from a patient;
detection means coupled to said input means for detecting QRS waveforms in said ECG signal and for generating timing data indicative of periods between consecutively received QRS waveforms;
frequency demodulation means coupled to said detection means for demodulating said timing data in real time and for generating a signal corresponding to a frequency modulating signal in said ECG signal, wherein said generated signal is used to provide said measure of vagal tone;
wherein said timing data comprises a sequence of fixed length pulses which are generated upon receipt of a QRS waveform; and
wherein said frequency demodulation means comprises a first integrator coupled to the detection means for receiving said fixed length pulses and a high pass filter and a low pass filter coupled separately to the first integrator for respectively receiving an output of the first integrator, an output of the high pass filter being coupled to a first voltage controlled oscillator via a second integrator and an output of the low pass filter being coupled to a second voltage controlled oscillator, outputs of the said first and second voltage controlled oscillators being coupled to respective inputs of a phase comparator arranged to generate at its output a signal indicative of the phase difference between the two input signals.
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16. An apparatus for providing a measure of vagal tone in a human or animal patient and comprising:
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input means for receiving an ECG signal obtained from a patient;
detection means coupled to said input means for detecting QRS waveforms in said ECG signal and for generating timing data indicative of periods between consecutively received QRS waveforms;
frequency demodulation means coupled to said detection means for demodulating said timing data in real time and for generating a signal corresponding to a frequency modulating signal in said ECG signal, wherein said generated signal is used to provide said measure of vagal tone; and
wherein the frequency demodulation means is a phase locked loop (PLL) incorporating a voltage controlled oscillator (VCO) tuned to a nominal constant heart rate.
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Specification