System and method for predicting ventricular tachycardia by adaptive high pass filter
First Claim
1. A ventricular tachycardia prediction system for use with an ECG input having cyclical characteristics comprising:
- means for periodically sampling the ECG input during each of a plurality of ECG cycles,means for storing signals representative of the ECG input for each corresponding sample time;
filter means for adaptively high pass filtering the signals for each ECG cycle, so as to provide a filter output systematically related to the high frequency content of the ECG input;
means for providing a reference signal;
means for comparing the filter output to the reference signal; and
means for indicating the prediction of ventricular tachycardia responsive to said means for comparing.
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Accused Products
Abstract
A ventricular tachycardia (VT) prediction system for use with an ECG input having cyclical characteristics. The ECG input is periodically sampled during each of a plurality of ECG cycles, and signals representative of the ECG input for each corresponding sample time are stored. A high pass filter adaptively filters the signals for each ECG cycle, so as to provide a filter output systematically related to the high frequency content of the ECG input. The adaptive filter produces segments which are uninfluenced by other samples so as to negate ringing. A reference signal is provided for VT prediction. The filter output is compared to the reference signal, and the prediction of ventricular tachycardia is indicated responsive to the comparison. In one embodiment the samples are averaged for a plurality of ECG cycles prior to generating the filter output. In another embodiment, the system determines the duration of the QRS portion of the ECG cycles prior to generating the filter output. In another embodiment, the system determines the duration of the QRS portion of the ECG signal, provides a second reference signal for VT prediction, and compares the determined duration to the second reference signal. A prediction of ventricular tachycardia is indicated responsive to the second comparison.
126 Citations
28 Claims
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1. A ventricular tachycardia prediction system for use with an ECG input having cyclical characteristics comprising:
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means for periodically sampling the ECG input during each of a plurality of ECG cycles, means for storing signals representative of the ECG input for each corresponding sample time; filter means for adaptively high pass filtering the signals for each ECG cycle, so as to provide a filter output systematically related to the high frequency content of the ECG input; means for providing a reference signal; means for comparing the filter output to the reference signal; and means for indicating the prediction of ventricular tachycardia responsive to said means for comparing. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A system, having X, Y, and Z ECG waveform inputs, for predicting ventricular tachycardia in a patient, said system comprising:
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means for sampling and storing voltage inputs from each of the X, Y, and Z ECG waveforms at a fixed rate of N samples per predefined time interval, means for identifying a peak value time point P for each of the X, Y, and Z ECG waveforms, adaptive filter means responsive to a spread of ±
l sample points about any center sampled point, comprisingmeans for deriving a filter output Qn responsive to the stored samples, where n is a running index, and Am are predefined filter constants such that ##EQU14## where (1) for filtering of n<
p+l then In+m =0 for 0>
n+m and for n+m>
N;(2) for filtering of P+l>
n>
p, then In+m =Ip for all n+m<
p; and(3) for filtering of n<
p, then In+m =Ip for all n+m>
p; andmeans for predicting the probable occurrence of ventricular tachycardia from the filter output.
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12. A method for predicting ventricular tachycardia in a patient from cyclically recurring ECG inputs, comprising the steps of:
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sampling and storing a plurality of points each ECG cycle at a fixed rate of N samples per cycle; identifying a reference point p of the waveform, filtering each sampled point with a spread of ±
l points about any center sampled point;deriving a filter output Qn responsive to the stored samples, where n is a running index and am are predefined filter constants, such that ##EQU15## (1) where for filtering of n>
p+l, then In+m =0 for 0>
n+m, and n+m>
N, and(2) where for filtering of p+l>
n>
P, then In+m =Ip for all n+m<
p; and(3) where for filtering of n<
p, then In+m =Ip for all n+m>
p;determining a predefined reference signal, comparing the filter output to said predefined reference signal and indicating the prediction of potential ventricular tachycardia responsive to said comparison.
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13. A method for predicting ventricular tachycardia from an ECG input waveform W comprising the steps of:
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determining a peak value p of the waveform W, sampling and storing the sampled values of the waveform W at a predefined rate; determining two reference sample positions Δ
1 and Δ
2;determining a filter output Q systematically related to the stored samples, where n is a running index of sample points, where 2l+1 is the spread of filter input samples analyzed, and where am are predetermined filter constants, such that ##EQU16## where (1) for filtering of n>
p+Δ
2 then Wn+m =Wp+Δ
2 for n+m<
p+Δ
2, and(2) for filtering of p+Δ
2 >
n>
p-Δ
1 then Wn+m =Wp+Δ
2 for n+m>
p+Δ
2 and Wn+m =Wp-Δ
1 for n+m<
p-Δ
1; and(3) for filtering of n<
p-Δ
1, then Wn+m =Wp-Δ
1 for n+m>
p-Δ
1;determining a reference signal, comparing the filter output to the reference signal, and indicating the prediction of ventricular tachycardia responsive to said comparison.
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14. A method for analyzing electrocardiograph signals to determine the presence or absence of a predetermined level of high frequency energy in the late QRS signal having X, Y, and Z parts, comprising the steps of:
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sampling a series of analog QRS signals at spaced time segments, converting each segment sample to a digital signal equivalent, applying a portion of said digital signals to an adaptive high pass filter; determining an arithmetic value of the amplitude of the output of said filter; and comparing said value with said predetermined level. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21)
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22. A system for analyzing electrocardiograph signals to determine the level of high frequency energy in the late QRS signal comprising:
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means for converting X, Y, and Z lead electrocardiographic input signals to digital signals representative of times spaced samples; means for examining said X, Y, and Z digital signals and selecting therefrom the QRS waveform portions thereof; means for signal averaging a multiplicity of said selected QRS waveforms for each of said X, Y, and Z inputs and providing composite, digital signals representative of the averaged X, Y, and Z QRS waveforms; high pass filter means having a finite impulse response; means for applying to said filter means the digital signals representative of the late portion of each of said X, Y, and Z QRS waveforms; means for providing a reference signal; and means for comparing the output of said filter means with said reference signal to determine the presence of a high frequency, low level, energy component in the filter output predicative of ventricular tachycardia. - View Dependent Claims (23, 24, 25, 26, 27, 28)
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Specification