Peak selection for self correlation analysis of cardiac rate in an implantable medical device
First Claim
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1. A method of analyzing cardiac signals in a 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 candidate peak having the least lag depth of the identified candidate amplitude peaks as a first candidate peak; 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;
wherein the first estimate of cardiac rate is generated by converting the first lag depth to a time interval and converting the time interval into a rate in response to finding that the picket test was passed by 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.
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Citations
20 Claims
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1. A method of analyzing cardiac signals in a 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 candidate peak having the least lag depth of the identified candidate amplitude peaks as a first candidate peak; 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; wherein the first estimate of cardiac rate is generated by converting the first lag depth to a time interval and converting the time interval into a rate in response to finding that the picket test was passed by the first candidate peak. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A cardiac monitoring or therapy device comprising:
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a 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 a candidate amplitude peak having the least lag depth of the identified candidate amplitude peaks; 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; wherein the operational circuitry is further configured such that the first estimate of cardiac rate is generated by converting the first lag depth to a time interval and converting the time interval into a rate in response to finding that the picket test was passed by the first candidate peak. - View Dependent Claims (12, 13, 14, 15, 16)
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17. A medical device comprising sensing electrodes for obtaining cardiac signals, sensing circuitry for analyzing obtained cardiac signals, 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 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 a candidate amplitude peak having the least lag depth of the identified candidate amplitude peaks; 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; and converting the first lag depth to a time interval and converting the time interval into a rate that serves as the first estimate of cardiac rate in response to finding that the picket test was passed by the first candidate peak. - View Dependent Claims (18, 19, 20)
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Specification