Cardiac rhythm management system using time-domain heart rate variability indicia
First Claim
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1. A method including:
- detecting heart contractions over a time period;
obtaining a time-domain first signal representing time intervals between the detected heart contractions;
filtering the first signal to obtain a time-domain second signal including frequency components substantially in a first frequency band, wherein the second signal is influenced by both sympathetic and parasympathetic components of an autonomic nervous system;
filtering the first signal to obtain a time-domain third signal including frequency components substantially in a second frequency band, wherein the third signal is influenced by the parasympathetic component of the autonomic nervous system and not substantially influenced by the sympathetic component of the autonomic nervous system;
obtaining a time domain variance of each of the second and third signals; and
providing an indication associated with a balance between the sympathetic and parasympathetic components of the autonomic nervous system based on a ratio between the time-domain variances of the second and third signals.
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Abstract
A cardiac rhythm management system that provides an indication of patient well-being based on the autonomic balance between the sympathetic and parasympathetic/vagal components of the autonomic nervous system, using time-domain processing of frequency components of a heart rate interval signal.
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Citations
32 Claims
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1. A method including:
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detecting heart contractions over a time period;
obtaining a time-domain first signal representing time intervals between the detected heart contractions;
filtering the first signal to obtain a time-domain second signal including frequency components substantially in a first frequency band, wherein the second signal is influenced by both sympathetic and parasympathetic components of an autonomic nervous system;
filtering the first signal to obtain a time-domain third signal including frequency components substantially in a second frequency band, wherein the third signal is influenced by the parasympathetic component of the autonomic nervous system and not substantially influenced by the sympathetic component of the autonomic nervous system;
obtaining a time domain variance of each of the second and third signals; and
providing an indication associated with a balance between the sympathetic and parasympathetic components of the autonomic nervous system based on a ratio between the time-domain variances of the second and third signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
squaring each of the second and third signals; and
lowpass filtering the squared second and third signals.
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5. The method of claim 1, further including lowpass filtering the ratioed variance of the second and third signals.
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6. The method of claim 1, in which providing an indication associated with an autonomic nervous system includes extracting a signal feature of the ratioed variance of the second and third signals.
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7. The method of claim 1, in which filtering the first signal to obtain a time-domain second signal includes bandpass filtering using a lowpass cutoff frequency that is approximately equal to 0.15 Hz and a highpass cutoff frequency that is approximately equal to 0.04 Hz.
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8. The method of claim 1, in which filtering the first signal to obtain a time-domain third signal includes bandpass filtering using a lowpass cutoff frequency that is approximately equal to 0.40 Hz and a highpass cutoff frequency that is approximately equal to 0.15 Hz.
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9. The method of claim 1, in which detecting heart contractions includes detecting ventricular heart contractions.
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10. The method of claim 1, further including providing therapy to the heart based on the indication associated with the balance between the sympathetic and parasympathetic components of the autonomic nervous system.
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11. The method of claim 10, in which providing therapy includes providing antitachyarrhythmia therapy.
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12. The method of claim 11, in which providing antitachyarrhythmia therapy includes providing antitachyarrhythmia pacing.
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13. The method of claim 11, in which providing antitachyarrhythmia therapy includes providing an antiarrhythmic drug.
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14. The method of claim 1, in which obtaining a time-domain first signal representing time intervals between the detected heart contractions includes:
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detecting R-wave peaks;
measuring time intervals between R-wave peaks;
providing a continuous-time R-R interval signal based on the measured time intervals between R-wave peaks; and
sampling the continuous-time R-R interval signal using a plurality of sample points that, when the sample points span a pair of R-R intervals, are weighted according to a time associated with each R-R interval in the pair of R-R intervals.
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15. A method including:
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detecting heart contractions over a time period;
obtaining a time-domain first signal representing time intervals between the detected heart contractions;
filtering the first signal to obtain a time-domain second signal including frequency components substantially in a first frequency band, wherein the second signal is influenced by both sympathetic and parasympathetic components of an autonomic nervous system;
filtering the first signal to obtain a time-domain third signal including frequency components substantially in a second frequency band, wherein the third signal is influenced by the parasympathetic component of the autonomic nervous system and not substantially influenced by the sympathetic component of the autonomic nervous system;
obtaining a time domain variance of each of the second and third signals; and
providing an indication associated with a balance between the sympathetic and parasympathetic components of the autonomic nervous system based on a ratio between the variances of the time-domain second and third signals, including selecting a time period on which the indication is based by comparing intervals between heart contractions, during the time period, to a predetermined criterion. - View Dependent Claims (16, 17)
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18. A method including:
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detecting heart contractions over a time period;
obtaining a time-domain first signal representing time intervals between the detected heart contractions;
bandpass filtering the first signal, using a lowpass cutoff frequency that is approximately equal to 0.15 Hz and a highpass cutoff frequency that is approximately equal to 0.04 Hz, to obtain a time-domain low frequency (LF) signal;
bandpass filtering the first signal, using a lowpass cutoff frequency that is approximately equal to 0.40 Hz and a highpass cutoff frequency that is approximately equal to 0.15 Hz, to obtain a time-domain high frequency (HF) signal; and
obtaining variances of the LF and HF signals; and
ratioing the variances of the LF and HF signals to obtain an LF/HF ratio signal. - View Dependent Claims (19, 20)
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21. A system including:
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a heart contraction detection module, providing a heart rate interval signal carrying information regarding intervals between heart contractions;
a low frequency (LF) bandpass filter, coupled to the detection module for receiving the heart rate interval signal, the LF bandpass filter providing a time-domain LF signal output that is influenced by both sympathetic and parasympathetic components of an autonomic nervous system;
a high frequency (HF) bandpass filter, coupled to the detection module for receiving the heart rate interval signal, the HF bandpass filter providing a time-domain HF signal output having higher frequency components than the LF signal output, the HF signal output being influenced by the parasympathetic component of the autonomic nervous system and not substantially influenced by the sympathetic component of the autonomic nervous system;
an LF variance module coupled to the LF bandpass filter for receiving the LF signal, the LF variance module providing a resulting LF variance signal;
a HF variance module, coupled to the HF bandpass filter for receiving the HF signal, the HF variance module providing a resulting HF variance signal; and
an autonomic balance indicator module, coupled to the LF and HF variance modules, and providing an indication of a balance between sympathetic and parasympathetic components of the autonomic nervous system based on a ratio between the LF and HF variance signals. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30)
a ratioing circuit, coupled to the LF and HF variance modules, and including a ratioing circuit output providing the LF/HF ratio; and
a peak detector, coupled to the ratioing circuit output, the peak detector configured to detect at least one of (a) at least one local maximum of the LF/HF ratio; and
(b) at least one local minimum of the LF/HF ratio.
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31. A system including:
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a heart contraction detection module, providing a heart rate interval signal carrying information regarding intervals between heart contractions;
first and second bandpass filters, coupled to the detection module for receiving the heart rate interval signal, the bandpass filters providing respective LF and HF time-domain bandpass filtered signal outputs;
LF and HF variance modules respectively coupled to the LF and HF bandpass filter outputs for providing respective LF and HF variances;
a ratioing circuit, coupled to the LF and HF variance modules, and including a ratioing circuit output providing an LF/HF ratio of the LF and HF variances;
an autonomic balance indicator module, coupled to the ratioing circuit, and providing an indication of a balance between sympathetic and parasympathetic components of an autonomic nervous system, based on the LF/HF ratio; and
an antitachyarrhythmia therapy module, adapted to be coupled to a heart, the therapy module providing antitachyarrhythmia therapy to the heart based at least in part on the indication of the balance between the sympathetic and parasympathetic components of the autonomic nervous system. - View Dependent Claims (32)
a peak detector, coupled to the ratioing circuit output, the peak detector configured to detect at least one of(a) at least one local maximum of the LF/HF ratio; and
(b) at least one local minimum of the LF/HF ratio.
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Specification