Detection of cardiac arrhythmias using correlation of a cardiac electrical signals and temporal data compression
First Claim
1. A method of detecting cardiac arrhythmias in a patient'"'"'s heart, comprising the steps of:
- sensing cardiac electrical signals when the heart is functioning in a known cardiac state;
characterizing said known cardiac state in a time sequence of template samples;
temporally compressing said time sequence of template samples;
storing said temporally compressed template samples;
monitoring a time sequence of cardiac electrical signal samples when the heart is functioning in an unknown cardiac state;
temporally compressing said unknown cardiac state samples monitored during said time sequence;
scan correlating said compressed unknown cardiac state samples with said stored compressed template samples to derive a correlation coefficient;
comparing said correlation coefficient with a threshold value;
classifying said unknown cardiac state within said known cardiac state when the correlation coefficient is greater than said threshold value, and classifying said unknown cardiac state outside said known cardiac state when the correlation coefficient is not greater than said threshold value, andhighpass filtering said sensed cardiac electrical signals when the heart is operating in each of said known cardiac state and said unknown cardiac state to substantially eliminate the mean amplitude of each of said temporally compressed template samples and said temporally compressed unknown cardiac state samples.
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Accused Products
Abstract
A method and apparatus for detecting cardiac arrhythmias in a patient'"'"'s heart is disclosed. The monitoring method and apparatus sense cardiac electrical signals when the heart is functioning in a known cardiac state, then characterize this known cardiac state by storing a temporally compressed template of time sequence samples. The method and apparatus allow testing during multiple different cardiac states and provide for storage of templates associated with each state. Subsequently, when the heart is functioning in an unknown cardiac state, the method and apparatus monitor cardiac electrical signals by temporally compressing samples and scan correlating these samples with the previously stored template sequences to derive correlation coefficients. The method and apparatus then use these correlation coefficients to characterize cardiac function.
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Citations
28 Claims
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1. A method of detecting cardiac arrhythmias in a patient'"'"'s heart, comprising the steps of:
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sensing cardiac electrical signals when the heart is functioning in a known cardiac state; characterizing said known cardiac state in a time sequence of template samples; temporally compressing said time sequence of template samples; storing said temporally compressed template samples; monitoring a time sequence of cardiac electrical signal samples when the heart is functioning in an unknown cardiac state; temporally compressing said unknown cardiac state samples monitored during said time sequence; scan correlating said compressed unknown cardiac state samples with said stored compressed template samples to derive a correlation coefficient; comparing said correlation coefficient with a threshold value; classifying said unknown cardiac state within said known cardiac state when the correlation coefficient is greater than said threshold value, and classifying said unknown cardiac state outside said known cardiac state when the correlation coefficient is not greater than said threshold value, and highpass filtering said sensed cardiac electrical signals when the heart is operating in each of said known cardiac state and said unknown cardiac state to substantially eliminate the mean amplitude of each of said temporally compressed template samples and said temporally compressed unknown cardiac state samples. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of detecting cardiac arrhythmias in a patient'"'"'s heart, comprising the steps of:
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sensing cardiac electrical signals when the heart is functioning in a known cardiac state; characterizing said known cardiac state in a time sequence of template samples; temporally compressing said time sequence of template samples; storing said temporally compressed template samples; monitoring a time sequence of cardiac electrical signal samples when the heart is functioning in an unknown cardiac state; temporally compressing said unknown cardiac state samples monitored during said time sequence; scan correlating said compressed unknown cardiac state samples with said stored compressed template samples to derive a correlation coefficient; comparing said correlation coefficient with a threshold value; and classifying said unknown cardiac state within said known cardiac state when the correlation coefficient is greater than said threshold value, and classifying said unknown cardiac state outside said known cardiac state when the correlation coefficient is not greater than said threshold value, wherein said step of characterizing said known cardiac state in a time sequence of template samples comprises the sub-steps of; sampling a first sequence of cardiac electrical signals sensed when the heart is functioning in a known cardiac state; storing said first sequence samples in a template memory; sampling and storing subsequent cardiac electrical signals; scan correlating said subsequent cardiac electrical signal samples with said template samples to derive a second correlation coefficient; comparing said second correlation coefficient with a second threshold value; if said second correlation coefficient is greater than said second threshold value, aligning said subsequent cardiac electrical signal samples in time; averaging said aligned subsequent cardiac electrical signal samples into said template; and repeating said sampling, storing, scan correlating, comparing, aligning, and averaging steps for a predetermined number of iterations. - View Dependent Claims (11, 12, 13)
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14. A method of detecting cardiac arrhythmias in a patient'"'"'s heart, comprising the steps of:
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sensing cardiac electrical signals when the heart is functioning in a known cardiac state; characterizing said known cardiac state in a time sequence of template samples; temporally compressing said time sequence of template samples; storing said temporally compressed template samples; monitoring a time sequence of cardiac electrical signal samples when the heart is functioning in an unknown cardiac state; temporally compressing said unknown cardiac state samples monitored during said time sequence; scan correlating said compressed unknown cardiac state samples with said stored compressed template samples to derive a correlation coefficient; comparing said correlation coefficient with a threshold value; and classifying said unknown cardiac state within said known cardiac state when the correlation coefficient is greater than said threshold value, and classifying said unknown cardiac state outside said known cardiac state when the correlation coefficient is not greater than said threshold value, wherein each of said temporally compressing steps comprises the sub-steps of; determining the differences between the most recent sample of said temporally compressed time sequence and each of a predetermined number of consecutive noncompressed samples of said sensed cardiac electrical signal sequence, wherein said predetermined number is a compression ratio; mutually comparing said differences to identify the sample in said sensed cardiac electrical signal sequence associated with the largest difference; and setting the current compressed sample to the value of the identified sample.
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15. Apparatus for detecting cardiac arrhythmias in a patient'"'"'s heart, comprising:
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means for sensing cardiac electrical signals when the heart is functioning in a known cardiac state; means for characterizing said known cardiac state in a time sequence of template samples; means for temporally compressing said time sequence of template samples; means for storing said temporally compressed template samples; means for monitoring a time sequence of cardiac electrical signal samples when the heart is functioning in an unknown cardiac state; means for temporally compressing said unknown cardiac state samples monitored during said time sequence; means for scan correlating said compressed unknown cardiac state samples with said stored compressed template samples to derive a correlation coefficient; means for comparing said correlation coefficient with a threshold value; means for classifying said unknown cardiac state within said known cardiac state when the correlation coefficient is greater than said threshold value, and classifying said unknown cardiac state outside said known cardiac state when the correlation coefficient is not greater than said threshold value; and means for highpass filtering said sensed cardiac electrical signals when the heart is operating in each of said known cardiac state and said unknown cardiac state to substantially eliminate the mean amplitude of each of said temporally compressed template samples and said temporally compressed unknown cardiac state samples. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23)
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24. Apparatus for detecting cardiac arrhythmias in a patient'"'"'s heart, comprising:
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means for sensing cardiac electrical signals when the heart is functioning in a known cardiac state; means for characterizing said known cardiac state in a time sequence of template samples; means for temporally compressing said time sequence of template samples; means for storing said temporally compressed template samples; means for monitoring a time sequence of cardiac electrical signal samples when the heart is functioning in an unknown cardiac state; means for temporally compressing said unknown cardiac state samples monitored during said time sequence; means for scan correlating said compressed unknown cardiac state samples with said stored compressed template samples to derive a correlation coefficient; means for comparing said correlation coefficient with a threshold value; and means for classifying said unknown cardiac state within said known cardiac state when the correlation coefficient is greater than said threshold value, and classifying said unknown cardiac state outside said known cardiac state when the correlation coefficient is not greater than said threshold value, wherein each of said temporally compressing means further comprises; means for determining the differences between the most recent sample of said temporally compressed time sequence and each of a predetermined number of consecutive noncompressed samples of said sensed cardiac electrical signal sequence, wherein said predetermined number is a compression ration; means for mutually comparing said differences to identify the sample in said sensed cardiac electrical signal sequence associated with the largest difference; and means for setting the current compressed sample to the value of the identified sample.
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25. Apparatus for detecting cardiac arrhythmias in a patient'"'"'s heart, comprising:
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means for sensing cardiac electrical signals when the heart is functioning in a known cardiac state; means for characterizing said known cardiac state in a time sequence of template samples; means for temporally compressing said time sequence of template samples; means for storing said temporally compressed template samples; means for monitoring a time sequence of cardiac electrical signal samples when the heart is functioning in an unknown cardiac state; means for temporally compressing said unknown cardiac state samples monitored during said time sequence; means for scan correlating said compressed unknown cardiac state samples with said stored compressed template samples to derive a correlation coefficient; means for comparing said correlation coefficient with a threshold value; and means for classifying said unknown cardiac state within said known cardiac state when the correlation coefficient is greater than said threshold value, and classifying said unknown cardiac state outside said known cardiac state when the correlation coefficient is not greater than said threshold value, wherein said means for characterizing said known cardiac state in a time sequence of template samples further comprises; means for sampling a first sequence of cardiac electrical signals sensed when the heart is functioning in a known cardiac state; means for storing said first sequence samples in a template memory; means for sampling and storing subsequent cardiac electrical signals; means for scan correlating said subsequent cardiac electrical signals samples with said template samples to derive a second correlation coefficient; means for comparing said second correlation coefficient with a second threshold value; means, operative when said second correlation coefficient is greater than said second threshold value, for aligning said subsequent cardiac electrical signal samples in time; means for averaging said aligned subsequent cardiac electrical signal samples into said template; and means for sequentially actuating said sampling, storing, scan correlating, comparing, aligning, and averaging means for a predetermined number of iterations. - View Dependent Claims (26, 27, 28)
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Specification