Tachyarrhythmia detection and discrimination based on curvature parameters
First Claim
1. An implantable cardiac rhythm management device comprising:
- an input circuit adapted to receive a sampled signal including sampled data points corresponding to cardiac electrical activity;
a controller coupled to the input circuit and adapted to compute a curvature series using the sample data points, identify lobes each being an excursion of more than a curvature threshold value from a baseline in the computed curvature series, generate a series of characteristic points each associated with a time of a lobe of the identified lobes in the curvature series, and determine a fundamental frequency of the sampled signal by autocorrelating a function of the series of characteristic points, wherein the curvature series includes curvatures each being a non-linear function of first and second derivatives of the sampled signal at one of the sample data points, and the controller is adapted to compute the first and second derivatives and the curvatures; and
a memory coupled to the controller and adapted to store the fundamental frequency.
1 Assignment
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Accused Products
Abstract
Estimating a frequency of a sampled cardiac rhythm signal and classifying the rhythm. The received signal is sampled and transformed into a curvature series. A lobe in the curvature series corresponds to a characteristic point in the sampled series. Characteristic points are selected based on a time of a lobe in the curvature series and, in one embodiment, an amplitude of the signal at the time of the lobe. A frequency of the sampled series is estimated by autocorrelating a function of the series of the characteristic points. In one embodiment, the function is a time difference function. The rhythm is classified by plotting the timewise proximity of characteristic points derived from an atrial signal with characteristic points derived from a ventricular signal. Regions of the plot are associated with a particular rhythm and the grouping of the data corresponds to the classification.
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Citations
25 Claims
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1. An implantable cardiac rhythm management device comprising:
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an input circuit adapted to receive a sampled signal including sampled data points corresponding to cardiac electrical activity; a controller coupled to the input circuit and adapted to compute a curvature series using the sample data points, identify lobes each being an excursion of more than a curvature threshold value from a baseline in the computed curvature series, generate a series of characteristic points each associated with a time of a lobe of the identified lobes in the curvature series, and determine a fundamental frequency of the sampled signal by autocorrelating a function of the series of characteristic points, wherein the curvature series includes curvatures each being a non-linear function of first and second derivatives of the sampled signal at one of the sample data points, and the controller is adapted to compute the first and second derivatives and the curvatures; and a memory coupled to the controller and adapted to store the fundamental frequency. - View Dependent Claims (2, 3, 4, 5)
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6. A method comprising:
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receiving sampled data points representative of a cardiac signal; calculating a series of curvatures each as a non-linear function of first and second derivatives of the cardiac signal at one of the sample data points; identifying lobes each being an excursion of more than a curvature threshold value from a baseline in the calculated series of curvatures; establishing a series of characteristic points each corresponding to a time of occurrence of a lobe of the identified lobes in the series of curvatures; using a processor to determine a frequency for the cardiac signal by autocorrelating a function of the series of characteristic points; and storing the frequency in a memory. - View Dependent Claims (7, 8, 9, 10, 11, 12)
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13. A method comprising:
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receiving a sampled input signal being a function of sensed cardiac electrical activity; using a processor to generate a curvature series by computing curvatures each as a non-linear function of first and second derivatives at a sample point of the sampled input signal; identifying lobes each being an excursion from a baseline in the curvatures series using a curvature threshold value; generating a series of characteristic points as a function of the curvature series, the characteristic points each associated with a lobe of the identified lobes in the curvature series and having a time as a function of a time of occurrence of the lobe of the identified lobes and a size as a function of an area of the lobe of the identified lobes; autocorrelating a function of the series of characteristic points to determine a fundamental frequency of the sampled input signal; and storing the fundamental frequency in a memory coupled to the processor. - View Dependent Claims (14, 15, 16, 17, 18)
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19. An article comprising a machine-accessible medium having associated data wherein the data, when accessed, results in a machine performing:
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receiving a sampled cardiac signal including sampled data points representative of the cardiac signal; generating a curvature series using the sampled data points by computing curvatures each as a non-linear function of first and second derivatives of the sampled cardiac signal at one of the sampled data points; identifying lobes each being an excursion of more than a curvature threshold value from a baseline in the curvature series; generating a series of characteristic points in the sampled cardiac signal, each characteristic point corresponding to a lobe of the identified lobes in the curvature series and having a time corresponding to a time of occurrence of the lobe of the identified lobes; determining a frequency by autocorrelating a function of the series of characteristic points, the frequency including a fundamental frequency of the sampled cardiac signal; and storing the frequency in a memory. - View Dependent Claims (20, 21)
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22. An article comprising a machine-accessible medium having associated data wherein the data, when accessed, results in a machine performing:
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receiving a first sampled signal including first sampled data points and a second sampled signal including second sampled data points, the first and second sampled signals each representing cardiac electrical activity for an epoch; generating a first curvature series using the first sampled data points by calculating curvatures each as a non-linear function of first and second derivatives of the first sampled signal at one of the first sampled data points; generating a second curvature series using the second sampled data points by calculating curvatures each being a non-linear function of first and second derivatives of the second sampled signal at one of the second sampled data points; identifying first lobes each being an excursion from a baseline in the first curvature series using a first curvature threshold value; identifying second lobes each being an excursion from a baseline in the second curvature series using a second curvature threshold value; generating a first series of characteristic points in the first sampled signal and a second series of characteristic points in the second sampled signal, each characteristic point in the first series of characteristic points corresponding to a lobe of the identified first lobes and having a time corresponding to a time of occurrence of the lobe of the identified first lobes, each characteristic point in the second series of characteristic points corresponding to a lobe of the identified second lobes and having a time corresponding to a time of occurrence of the lobe of the identified second lobes; generating a classification of the epoch based on a plot of timewise occurrence of first series characteristic points relative to timewise occurrence of second series characteristic points and a separation contour; and storing the classification in a memory. - View Dependent Claims (23, 24, 25)
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Specification