Apparatus and method for automatic sensing threshold determination in cardiac pacemakers
First Claim
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1. An automatic sensing system for an implantable cardiac rhythm management device comprising in combination:
- (a) amplifying and filtering means for receiving ECG signals and noise signals, said amplifying and filtering means including(i) a variable gain amplifier having a first input terminal coupled to receive said ECG signals and said noise signals, a second input terminal for receiving a gain adjust signal and an output terminal;
(ii) bandpass filter means coupled to said output terminal for attenuating said noise signals while passing said ECG signals;
(iii) rectifier means coupled to said bandpass filter means for converting said ECG signals of either polarity to unipolar signals; and
(iv) low pass filter means coupled to said rectifier means for attenuating said noise signals whose frequencies are above a predetermined cut-off frequency;
(b) trip point comparator means having a signal input terminal, a trip point input terminal and an output terminal, said signal input terminal being coupled to an output of said low pass filter means, said trip point comparator producing an indication of a detected R or Q wave signal at said output terminal thereof when said output from said low pass filter means exceeds an adjustable trip point value applied to said trip point input terminal;
(c) peak detector means coupled to receive the output of said low pass filter means for producing a voltage indicative of the peak value of said R or P wave signal and the peak value of noise signals occurring between successive R or P wave signals;
(d) means coupled to said peak detector means for periodically computing said trip point value as a function of said peak value of said R or P wave signals and said noise signals occurring between successive R or P wave signals; and
(e) means for applying said trip point value to said trip point input terminal.
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Abstract
An automatic sensing system for an implantable cardiac rhythm management device comprises a variable gain amplifier and associated filters where the gain of the amplifier is adjusted as a function of the peak amplitude of a cardiac depolarization signal (either a P-wave or an R-wave) and especially the relationship of the peak value to a maximum value dictated by the circuit'"'"'s power supply rail. The trip point comparator has its trip point adjusted as a function of the difference between the detected peak value of the signal of interest and the peak value of noise not eliminated by the filtering employed.
271 Citations
16 Claims
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1. An automatic sensing system for an implantable cardiac rhythm management device comprising in combination:
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(a) amplifying and filtering means for receiving ECG signals and noise signals, said amplifying and filtering means including (i) a variable gain amplifier having a first input terminal coupled to receive said ECG signals and said noise signals, a second input terminal for receiving a gain adjust signal and an output terminal; (ii) bandpass filter means coupled to said output terminal for attenuating said noise signals while passing said ECG signals; (iii) rectifier means coupled to said bandpass filter means for converting said ECG signals of either polarity to unipolar signals; and (iv) low pass filter means coupled to said rectifier means for attenuating said noise signals whose frequencies are above a predetermined cut-off frequency; (b) trip point comparator means having a signal input terminal, a trip point input terminal and an output terminal, said signal input terminal being coupled to an output of said low pass filter means, said trip point comparator producing an indication of a detected R or Q wave signal at said output terminal thereof when said output from said low pass filter means exceeds an adjustable trip point value applied to said trip point input terminal; (c) peak detector means coupled to receive the output of said low pass filter means for producing a voltage indicative of the peak value of said R or P wave signal and the peak value of noise signals occurring between successive R or P wave signals; (d) means coupled to said peak detector means for periodically computing said trip point value as a function of said peak value of said R or P wave signals and said noise signals occurring between successive R or P wave signals; and (e) means for applying said trip point value to said trip point input terminal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. An automatic sensing system for an implantable rhythm management device, comprising in combination:
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(a) variable gain amplifier means having an input terminal and an output terminal, said input terminal receiving ECG and noise signals from the body; (b) signal processing means coupled to said output terminal of said amplifier means for attenuating noise and T-wave components of said ECG signals and for converting R-waves in said ECG signals of either polarity to a unipolar representation thereof; (c) peak detecting means coupled to said signal processing means for measuring the peak value of said unipolar representations of said R-waves and peak values of said noise signals in the output from said signal processing means and producing voltage signals proportional to each; (d) comparator means coupled to the output from said signal processing means, said comparator means having an adjustable trip point; and (e) trip point determining means coupled to receive said voltage signals from the output of said peak detecting means for adjusting said trip point of said comparable means as a function of said peak value of said unipolar representations of R-waves and of noise signals said trip point determining means including delay means for enhancing rejection of said T-waves and noise signals whose frequencies are below the frequency of said R-waves. - View Dependent Claims (15, 16)
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Specification