Data compression of cardiac electrical signals using scanning correlation and temporal data compression
First Claim
1. A method of data compressing and storing cardiac electrical signals which are sensed from a patient'"'"'s heart, comprising the steps of:
- sensing cardiac electrical signals when the heart is functioning in at least one known cardiac state;
characterizing each of said at least one known cardiac states in a time sequence of template samples;
temporally compressing and storing each of said time sequences of template samples;
monitoring a time sequence of cardiac electrical signal samples when the heart is functioning in an unknown cardiac state by sampling and temporally compressing said unknown cardiac state samples, scan correlating said compressed unknown cardiac state samples with at least one of said stored compressed template sample sequences to derive correlation coefficients associated with each of said temporally compressed unknown cardiac state samples and each of said temporally compressed template samples in said at least one stored temporally compressed template sample sequence, and mutually comparing said derived correlation coefficients associated with each of said unknown cardiac state samples and each of said template samples;
classifying each cf said unknown cardiac state time sequences of cardiac electrical signal samples as included or excluded from each of said known cardiac states on the basis of the results of said mutually comparing step and codifying the results of said classifying step;
determining a fiducial time for each of said unknown cardiac state sequences on the basis of the results of said mutually comparing step; and
storing a record of said codifications and associated fiducial times in a memory.
2 Assignments
0 Petitions
Accused Products
Abstract
A method and apparatus for storing a representation of a cardiac signal by compressing the data using scan correlation and temporal data compression techniques. The method and apparatus sense cardiac signals when the heart is functioning in a known cardiac state, then characterize this known state by storing a temporally compressed template of time sequence samples. The method and apparatus may perform testing for multiple different cardiac states and store templates associated with each state. Subsequently when the heart is functioning in an unknown cardiac state, the method and apparatus monitor cardiac signals by temporally compressing samples and scan correlating these samples with the previously stored templates to derive correlation coefficients. These correlation coefficients are a basis for identifying and classifying cardiac signal waveforms. For waveforms which correlate highly with a particular template, analysis of the timing of the maximum correlation coefficient provides a fiducial time which designates the time relationship of waveforms within different cardiac cycles. The method and apparatus store information in the form of templates, fiducial timing markers, and waveform occurrence counts. This data provides the information necessary to subsequently reproduce a long-term signal record.
-
Citations
26 Claims
-
1. A method of data compressing and storing cardiac electrical signals which are sensed from a patient'"'"'s heart, comprising the steps of:
-
sensing cardiac electrical signals when the heart is functioning in at least one known cardiac state; characterizing each of said at least one known cardiac states in a time sequence of template samples; temporally compressing and storing each of said time sequences of template samples; monitoring a time sequence of cardiac electrical signal samples when the heart is functioning in an unknown cardiac state by sampling and temporally compressing said unknown cardiac state samples, scan correlating said compressed unknown cardiac state samples with at least one of said stored compressed template sample sequences to derive correlation coefficients associated with each of said temporally compressed unknown cardiac state samples and each of said temporally compressed template samples in said at least one stored temporally compressed template sample sequence, and mutually comparing said derived correlation coefficients associated with each of said unknown cardiac state samples and each of said template samples; classifying each cf said unknown cardiac state time sequences of cardiac electrical signal samples as included or excluded from each of said known cardiac states on the basis of the results of said mutually comparing step and codifying the results of said classifying step; determining a fiducial time for each of said unknown cardiac state sequences on the basis of the results of said mutually comparing step; and storing a record of said codifications and associated fiducial times in a memory. - View Dependent Claims (2, 3, 4, 9, 10, 11, 13)
-
-
5. A method according to claim 5, wherein said step of characterizing said known cardiac state in a time sequence of template samples comprises the substeps 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 template correlation coefficient; comparing said template correlation coefficient with a template threshold value; if said template correlation coefficient is greater than said 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 and storing, scan correlating, comparing, aligning, and averaging steps for a predetermined number of iterations. - View Dependent Claims (6, 7, 8)
-
-
12. A method according to claim further comprising the steps of:
-
locating an R wave in said sequence of cardiac electrical signals; and aligning said first sequence samples in the template memory to that the R wave sample is stored in a predetermined sample location.
-
-
14. An apparatus for data compressing and storing cardiac electrical signals which are sensed from a patient'"'"'s heart, comprising:
-
means for sensing cardiac electrical signals when the heart is functioning in at least one known cardiac state; means for characterizing each of said at least one known cardiac states in a time sequence of template samples; means for temporally compressing and storing each of said time sequences of template samples; means for monitoring a time sequence of cardiac electrical signal samples when the heart is functioning in an unknown cardiac state, said monitoring means including means for sampling and temporally compressing said unknown cardiac state samples, means for scan correlating said compressed unknown cardiac state samples with at least one of said stored compressed template sample sequences to derive correlation coefficients associated with each of said temporally compressed unknown cardiac state samples and each of said temporally compressed template samples in said at least one stored temporally compressed template sample sequence, and means for mutually comparing said derived correlation coefficients associated with each of said unknown cardiac state samples and each of said template samples; means for classifying each of said unknown cardiac state time sequences of cardiac electrical signal samples as included or excluded from each of said known cardiac states on the basis of the results of the comparison made by said mutually comparing means, said classifying means including means for codifying the results of the classification made by said classifying means; means for determining a fiducial time for each of said unknown cardiac state sequences on the basis of the results of the comparison made by said mutually comparing means; and means for storing a record of said codifications and associated fiducial times in a memory. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
-
Specification