Signal averaging of cardiac electrical signals using temporal data compression and scanning correlation
First Claim
1. A method of aligning cardiac electrical signal waveforms from a patient'"'"'s heart to facilitate signal averaging, comprising the steps of:
- sensing and sampling cardiac electrical signals and, in response thereto, determining a heart rate for identifying the patient'"'"'s cardiac state;
when the patient'"'"'s heart is functioning in a known cardiac state, storing a time sequence of template samples, temporally compressing said time sequence of template samples, and storing a time sequence of said temporally compressed template samples;
monitoring subsequent cardiac electrical signals by storing a time sequence of cardiac signal samples, temporally compressing said time sequence of cardiac signal samples, and storing a time sequence of temporally compressed cardiac signal samples;
determining a coarse alignment timing marker for a cardiac cycle of said subsequent cardiac electrical signals by mutually scan correlating said temporally compressed cardiac signal samples with said temporally compressed template samples, and by comparing resulting correlation coefficients to locate a maximum correlation coefficient indicative of signal alignment of said compressed template with said compressed cardiac signal; and
determining a fine alignment timing marker for said cardiac cycle of subsequent cardiac electrical signals by mutually scan correlating those of said noncompressed cardiac signal samples which are closely adjacent to samples which correspond to the maximum correlation coefficient with those of said noncompressed template samples which are closely adjacent to samples which correspond to the maximum correlation coefficient, and by comparing resulting correlation coefficients to locate a maximum correlation coefficient indicative of signal alignment of said noncompressed template with said noncompressed cardiac signal.
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Accused Products
Abstract
A method and apparatus for aligning periodic cardiac signal waveforms for the purpose of signal averaging over a number of cardiac cycles. The aligning method and apparatus sense cardiac electrical signals over a number of cardiac cycles, store a template characterizing these signals, reduce the data rate of the same sensed signals by temporal data compression, and store a compressed template sequence. Subsequently, the method and apparatus perform signal averaging by monitoring cardiac electrical signals, storing samples of these signals, temporally compressing these samples and scan correlating the compressed samples with the previously stored compressed template sequence to derive correlation coefficients. Thereafter, the method and apparatus utilize the maximum correlation coefficient to roughly align the monitored waveform with the averaged signal, and then they scan correlate a portion of the noncompressed monitored waveform adjacent to the maximum correlation coefficient with a corresponding portion of the non-compressed template to provide precise alignment of the monitored waveform with the averaged signal.
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Citations
26 Claims
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1. A method of aligning cardiac electrical signal waveforms from a patient'"'"'s heart to facilitate signal averaging, comprising the steps of:
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sensing and sampling cardiac electrical signals and, in response thereto, determining a heart rate for identifying the patient'"'"'s cardiac state; when the patient'"'"'s heart is functioning in a known cardiac state, storing a time sequence of template samples, temporally compressing said time sequence of template samples, and storing a time sequence of said temporally compressed template samples; monitoring subsequent cardiac electrical signals by storing a time sequence of cardiac signal samples, temporally compressing said time sequence of cardiac signal samples, and storing a time sequence of temporally compressed cardiac signal samples; determining a coarse alignment timing marker for a cardiac cycle of said subsequent cardiac electrical signals by mutually scan correlating said temporally compressed cardiac signal samples with said temporally compressed template samples, and by comparing resulting correlation coefficients to locate a maximum correlation coefficient indicative of signal alignment of said compressed template with said compressed cardiac signal; and determining a fine alignment timing marker for said cardiac cycle of subsequent cardiac electrical signals by mutually scan correlating those of said noncompressed cardiac signal samples which are closely adjacent to samples which correspond to the maximum correlation coefficient with those of said noncompressed template samples which are closely adjacent to samples which correspond to the maximum correlation coefficient, and by comparing resulting correlation coefficients to locate a maximum correlation coefficient indicative of signal alignment of said noncompressed template with said noncompressed cardiac signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. Apparatus for aligning cardiac electrical signal waveforms from a patient'"'"'s heart to facilitate signal averaging, comprising:
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means for sensing and sampling cardiac electrical signals and, in response thereto, determining a heart rate for identifying the patient'"'"'s cardiac state; means, activated when said heart rate determining means determines that the patient'"'"'s heart is functioning in a known cardiac state, for storing a time sequence of template samples, temporally compressing said time sequence of template samples, and storing a time sequence of said temporally compressed template samples; means for monitoring subsequent cardiac electrical signals by storing a time sequence of cardiac signal samples, temporally compressing said time sequence of cardiac signal samples, and storing a time sequence of temporally compressed cardiac signal samples; means for determining a coarse alignment timing marker for a cardiac cycle of said subsequent cardiac electrical signals, said means including means for mutually scan correlating said temporally compressed cardiac signal samples with said temporally compressed template samples, and means for comparing resulting correlation coefficients to locate a maximum correlation coefficient indicative of signal alignment of said compressed template with said compressed cardiac signal; and means for determining a fine alignment timing marker for said cardiac cycle of subsequent cardiac electrical signals, said means including means for mutually scan correlating those of said noncompressed cardiac signal samples which are closely adjacent to cardiac signal samples which correspond to said maximum correlation coefficient with those of said noncompressed template samples which are closely adjacent to template samples which correspond to said maximum correlation coefficient, and means for comparing resulting correlation coefficients to locate a maximum correlation coefficient indicative of signal alignment of said noncompressed template with said noncompressed cardiac signal. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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Specification