Adaptive method and apparatus for extracting an evoked response component from a sensed cardiac signal by suppressing electrode polarization components
First Claim
1. In a method for suppressing electrode polarization components in a sensed cardiac signal, wherein a heart is stimulated by delivering an electrical signal to said heart which, if successful, produces an evoked response by said heart, wherein electrical activity is sensed in said heart after delivering said electrical signal and obtaining a sensed cardiac signal including a polarization component, and if stimulation was successful, an evoked response component, the improvement comprising:
- (a) applying an autocorrelation function to said sensed cardiac signalto obtain an autocorrelated signal;
(b) normalizing said sensed cardiac signal and said autocorrelated signal relative to each other; and
(c) forming a difference between the normalized sensed cardiac signal and the normalized autocorrelated signal and thereby extracting said evoked response component if present.
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Abstract
In a method and apparatus for suppressing electrode polarization components in a sensed cardiac signal, the sensed cardiac signal is added to either a differentiated or autocorrelated sensed cardiac signal and a difference is formed between the original sensed cardiac signal and the autocorrelated or differentiated signal, thereby extracting an evoked response component from the sensed cardiac signal, the evoked response component otherwise being overshadowed by the much higher-amplitude polarization component.
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Citations
21 Claims
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1. In a method for suppressing electrode polarization components in a sensed cardiac signal, wherein a heart is stimulated by delivering an electrical signal to said heart which, if successful, produces an evoked response by said heart, wherein electrical activity is sensed in said heart after delivering said electrical signal and obtaining a sensed cardiac signal including a polarization component, and if stimulation was successful, an evoked response component, the improvement comprising:
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(a) applying an autocorrelation function to said sensed cardiac signal to obtain an autocorrelated signal; (b) normalizing said sensed cardiac signal and said autocorrelated signal relative to each other; and (c) forming a difference between the normalized sensed cardiac signal and the normalized autocorrelated signal and thereby extracting said evoked response component if present. - View Dependent Claims (2, 3, 4, 5, 6)
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- 7. A method as claimed in claim I wherein step (b) comprises setting respective maxima of said sensed cardiac signal and said autocorrelated signal to a common value.
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9. In an apparatus for suppressing electrode polarization components in a sensed cardiac signal, including means for stimulating a heart by delivering an electrical signal to said heart which, if successful, produces an evoked response by said heart, means for sensing electrical activity in said heart after delivering said electrical signal and obtaining a sensed cardiac signal including a polarization component, and if stimulation was successful, an evoked response component, the improvement comprising:
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means for applying an autocorrelation function to said sensed cardiac signal to obtain an autocorrelated signal; means for normalizing said sensed cardiac signal and said autocorrelated signal relative to each other; and means for forming a difference between the normalized sensed cardiac signal and the normalized autocorrelated signal and thereby extracting said evoked response component, if present. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17)
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18. In a method for suppressing electrode polarization components in a sensed cardiac signal, wherein a heart is stimulated by delivering an electrical signal to said heart which, if successful, produces an evoked response by said heart, wherein electrical activity is sensed in said heart after delivering said electrical signal and obtaining a sensed cardiac signal including a polarization component, and if stimulation was successful, an evoked response component, the improvement comprising:
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(a) low pass filtering said sensed cardiac signal to obtain a low pass filtered signal; (b) differentiating said low pass filtered signal to obtain a differentiated signal; (c) adding said low pass filtered signal and said differentiated signal to obtain a sum; (d) differentiating said sum to obtain a differentiated sum; and (e) analyzing said differentiated sum to identify at least one signal parameter therein indicative of a presence of an evoked response in said sensed cardiac signal. - View Dependent Claims (19, 21)
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20. In an apparatus for suppressing electrode polarization components in a sensed cardiac signal, including means for stimulating a heart by delivering an electrical signal to said heart which, if successful, produces an evoked response by said heart, means for sensing electrical activity in said heart after delivering said electrical signal and obtaining a sensed cardiac signal including a polarization component, and if stimulation was successful, an evoked response component, the improvement comprising:
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means for low pass filtering said sensed cardiac signal to obtain a low pass filtered signal; means for differentiating said low pass filtered signal to obtain a differentiated signal; means for adding said low pass filtered signal and said differentiated signal to obtain a sum; means for differentiating said sum to obtain a differentiated sum; and means for analyzing said differentiated sum to identify at least one signal parameter therein indicative of a presence of an evoked response in said sensed cardiac signal.
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Specification