Peak selection for self correlation analysis of cardiac rate in an implantable medical devices
First Claim
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1. A method of analyzing cardiac signals in an implantable medical device having a plurality of electrodes for sensing cardiac signals coupled to operational circuitry for at least performing analysis of sensed cardiac signals, the method comprising:
- generating a self-correlation function from the sensed cardiac signals, the self-correlation function having amplitudes as a function of lag depth; and
identifying amplitude peaks in the self-correlation function and finding a first estimate of cardiac rate by;
identifying one or more candidate amplitude peaks each having lag depths;
selecting a first candidate peak having a first lag depth by choosing either;
a candidate peak having the least lag depth of the identified candidate peaks, ora candidate peak having an amplitude that is larger than that of the candidate peak with the least lag depth by at least a first margin and which corresponds to a cardiac rate exceeding a rate threshold; and
applying a picket test to the first candidate peak by determining whether at least one additional peak appears at a second lag depth that is a multiple of the lag depth of the first candidate peak and, if so, finding that the picket test is passed for the first candidate peak.
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Abstract
Self-correlation enhancements and implementations are described. In particular, certain examples demonstrate the use of a peak selector to identify peaks of a self-correlation function which serve as candidate cardiac rates for an implantable medical device. The approach may enable an alternative calculation of cardiac rate in an implantable medical device as a stand-alone rate detector or as a double-check of other rate calculations.
27 Citations
20 Claims
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1. A method of analyzing cardiac signals in an implantable medical device having a plurality of electrodes for sensing cardiac signals coupled to operational circuitry for at least performing analysis of sensed cardiac signals, the method comprising:
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generating a self-correlation function from the sensed cardiac signals, the self-correlation function having amplitudes as a function of lag depth; and identifying amplitude peaks in the self-correlation function and finding a first estimate of cardiac rate by; identifying one or more candidate amplitude peaks each having lag depths; selecting a first candidate peak having a first lag depth by choosing either; a candidate peak having the least lag depth of the identified candidate peaks, or a candidate peak having an amplitude that is larger than that of the candidate peak with the least lag depth by at least a first margin and which corresponds to a cardiac rate exceeding a rate threshold; and applying a picket test to the first candidate peak by determining whether at least one additional peak appears at a second lag depth that is a multiple of the lag depth of the first candidate peak and, if so, finding that the picket test is passed for the first candidate peak. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. An implantable cardiac device comprising:
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an implantable canister housing operational circuitry for performing cardiac signal analysis; and a plurality of electrodes coupled to the operational circuitry to provide cardiac signals thereto; wherein the operational circuitry is configured to perform a method of cardiac signal analysis comprising; generating a self-correlation function from the sensed cardiac signals, the self-correlation function having amplitudes as a function of lag depth; and identifying amplitude peaks in the self-correlation function and finding a first estimate of cardiac rate by; identifying one or more candidate amplitude peaks each having lag depths; selecting a first candidate peak having a first lag depth by choosing either; a candidate peak having the least lag depth of the identified candidate peaks, or a candidate peak having an amplitude that is larger than that of the candidate peak with the least lag depth by at least a first margin and which corresponds to a cardiac rate exceeding a rate threshold; and applying a picket test to the first candidate peak by determining whether at least one additional peak appears at a second lag depth that is a multiple of the lag depth of the first candidate peak and, if so, finding that the picket test is passed for the first candidate peak. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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19. An implantable medical device comprising sensing circuitry and a processor and a non-transitory medium with instructions contained therein for implementation by the processor, the processor configured to operate on the instructions to use the sensing circuitry and therapy output circuitry as follows:
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generating a self-correlation function from the sensed cardiac signals, the self-correlation function having amplitudes as a function of lag depth; and identifying amplitude peaks in the self-correlation function and finding a first estimate of cardiac rate by; identifying one or more candidate amplitude peaks each having lag depths; selecting a first candidate peak having a first lag depth by choosing either; a candidate peak having the least lag depth of the identified candidate peaks, or a candidate peak having an amplitude that is larger than that of the candidate peak with the least lag depth by at least a first margin and which corresponds to a cardiac rate exceeding a rate threshold; and applying a picket test to the first candidate peak by determining whether at least one additional peak appears at a second lag depth that is a multiple of the lag depth of the first candidate peak and, if so, finding that the picket test is passed for the first candidate peak. - View Dependent Claims (20)
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Specification