# US 9,872,652 B2 · Method and apparatus for heart rate monitoring using an electrocardiogram sensor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,872,652 B2 - Document ID: US9872652B2 - Status: Granted - Kind: B2 - Application number: 15/178,218 - Filed: 2016-06-09 - Published: 2016-12-15 - Granted: 2018-01-23 - Earliest claimed: 2015-06-09 - Assignees: University of Connecticut - Applicants: University of Connecticut - Inventors: Seyed M. A. Salehizadeh; Ki H. Chon; Yeonsik Noh - Web page: https://patentgrep.com/patent/US9872652B2 ## CPC - A61B 5/721: {using a separate sensor to detect motion or using motion information derived from signals other than the physiological signal to be measured} - A61B 5/0205: Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition - A61B 5/02416: {using photoplethysmograph signals, e.g. generated by infrared radiation (A61B5/14552 takes precedence)} - A61B 5/02427: {Details of sensor} - A61B 5/02438: {with portable devices, e.g. worn by the patient} - A61B 5/0245: by using sensing means generating electric signals, {i.e. ECG signals} - A61B 5/347: Detecting the frequency distribution of signals - A61B 5/7239: {using differentiation including higher order derivatives} - A61B 5/725: {using specific filters therefor, e.g. Kalman or adaptive filters (specific diagnostics methods using using bioelectric or biomagnetic signals A61B5/316)} - A61B 5/7253: {characterised by using transforms} - A61B 5/0077: {Devices for viewing the surface of the body, e.g. camera, magnifying lens} - A61B 5/02405: {Determining heart rate variability} - A61B 5/1102: {Ballistocardiography} - A61B 5/14552: {Details of sensors specially adapted therefor} - A61B 5/361: Detecting fibrillation - A61B 5/363: Detecting tachycardia or bradycardia - A61B 5/6824: {Arm or wrist} - A61B 5/7275: {Determining trends in physiological measurement data; Predicting development of a medical condition based on physiological measurements, e.g. determining a risk factor} - A61B 2503/10: Athletes - A61B 2505/07: Home care - A61B 2505/09: Rehabilitation or training - A61B 2562/0219: Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) ## Abstract A method and corresponding apparatus employ a time-varying spectral analysis approach for reconstructing an electrocardiogram (ECG) signal that includes motion artifacts. The motion artifacts are produced by motion of an ECG sensor relative to a sensing location. The time-varying spectral analysis based approach enables the ECG signal to be reconstructed with accuracy by suppressing the motion artifacts. Example applications for the method and corresponding apparatus include ECG-based heart rate monitoring in wearable devices for fitness tracking and health monitoring even during intense physical activities. ## Claims ### Claim 1 A method for reconstructing a heart-related signal output by a biomedical sensor, the method comprising: pre-processing the heart-related signal to produce a pre-processed heart-related signal; reconstructing a representation of the heart-related signal to produce a reconstructed representation of the heart-related signal, the reconstructing based on a time-varying spectral analysis of the pre-processed heart-related signal, the heart-related signal including motion artifacts, the motion artifacts being signal artifacts produced by movement of the biomedical sensor relative to a sensing location, the pre-processing reducing the motion artifacts in the pre-processed heart-related signal for the reconstructing, the heart-related signal being an electrocardiogram (ECG) signal; and outputting the reconstructed representation of the heart-related signal. ### Claim 2 (depends on 1) The method of claim 1, wherein the biomedical sensor is an electrocardiogram (ECG) sensor. ### Claim 3 (depends on 1) The method of claim 1, wherein the reconstructing further reduces the motion artifacts reduced by the pre-processing. ### Claim 4 (depends on 1) The method of claim 1, wherein the pre-processing includes down-sampling the heart-related signal to produce a down-sampled heart-related signal, the down-sampling being at a sampling rate less than an original sampling rate. ### Claim 5 (depends on 4) The method of claim 4, wherein: the time-varying spectral analysis is based on a frequency resolution; and the down-sampling affects the frequency resolution of the time-varying spectral analysis. ### Claim 6 (depends on 4) The method of claim 4, wherein the pre-processing includes computing a derivative of the down-sampled heart-related signal to reduce the motion artifacts. ### Claim 7 (depends on 6) The method of claim 6, wherein the pre-processing further includes computing an absolute value of the derivative to further reduce the motion artifacts. ### Claim 8 (depends on 1) The method of claim 1, wherein the time-varying spectral analysis includes computing a time-frequency spectrum (TFS) of the pre-processed heart-related signal. ### Claim 9 (depends on 8) The method of claim 8, wherein the TFS computed is a 3-dimensional spectra including a time-varying amplitude or power distribution with respect to time and frequency. ### Claim 10 (depends on 8) The method of claim 8, wherein the TFS computed is a time-varying power spectral density (PSD). ### Claim 11 (depends on 8) The method of claim 8, further including limiting the TFS computed to a given frequency range. ### Claim 12 (depends on 11) The method of claim 11, wherein the given frequency range is 0.5 Hz to 3 Hz. ### Claim 13 (depends on 8) The method of claim 8, wherein: the TFS is computed for each shift of a windowed data segment of the pre-processed heart-related signal; and the heart related signal is reconstructed for each shift of the windowed data segment. ### Claim 14 (depends on 13) The method of claim 13, wherein, at each shift of the windowed data segment subsequent to an initial windowed data segment, the method further includes: retaining up to a pre-determined number of frequency spectra to produce a subset of frequency spectra; and selecting a frequency component to produce a selected frequency component for the reconstructing, the selected frequency component selected from amongst frequency components of the subset of frequency spectra and a previous frequency component, the previous frequency component having been selected for a previous shift of the windowed data segment to reconstruct the heart-related signal for the previous shift. ### Claim 15 (depends on 1) The method of claim 1, wherein the time-varying spectral analysis is a first time-varying spectral analysis and wherein the reconstructing is further based on a second time-varying spectral analysis of a motion signal, the motion signal output by a motion sensor and representative of the motion artifacts in the heart-related signal. ### Claim 16 (depends on 15) The method of claim 15, further including employing the second time-varying spectral analysis of the motion signal to produce a movement classification of the movement, and wherein the reconstructing is further based on the classification of the movement. ### Claim 17 (depends on 15) The method of claim 15, wherein the heart-related signal and the motion signal are output, concurrently. ### Claim 18 (depends on 15) The method of claim 15, wherein the biomedical sensor and the motion sensor are co-located. ### Claim 19 (depends on 15) The method of claim 15, wherein the motion sensor is an accelerometer. ### Claim 20 (depends on 1) The method of claim 1, further comprising employing the reconstructed representation to determine a heart rate estimate. ### Claim 21 (depends on 1) The method of claim 1, further comprising employing the reconstructed representation to determine a heart rate variability (HRV) estimate. ### Claim 22 (depends on 1) The method of claim 1, further comprising employing the reconstructed representation to detect or predict a heart-related ailment, the heart-related ailment including at least one of a heart rate variability (HRV) condition, atrial fibrillation condition, congestive heart failure condition, and tachycardia condition. ### Claim 23 (depends on 1) The method of claim 1, wherein the pre-processing, the reconstructing, and the outputting are performed in real-time with respect to outputting of the heart-related signal by the biomedical sensor. ### Claim 24 (depends on 1) The method of claim 1, wherein the pre-processing, the reconstructing, and the outputting are performed in non-real-time with respect to outputting of the heart-related signal by the biomedical sensor. ### Claim 25 An apparatus for reconstructing a heart-related signal output by a biomedical sensor, the apparatus comprising: a pre-processing unit configured to pre-process the heart-related signal to produce a pre-processed heart-related signal; a reconstruction unit configured to reconstruct a representation of the heart-related signal to produce a reconstructed representation of the heart-related signal, the reconstructing based on a time-varying spectral analysis of the pre-processed heart-related signal, the heart-related signal including motion artifacts, the motion artifacts being signal artifacts produced by movement of the biomedical sensor relative to a sensing location, the pre-processing unit reducing the motion artifacts in the pre-processed heart-related signal for the reconstructing, the heart-related signal being an electrocardiogram (ECG) signal; and an output unit configured to output the reconstructed representation of the heart-related signal. ### Claim 26 (depends on 25) The apparatus of claim 25, wherein the biomedical sensor is an electrocardiogram (ECG) sensor. ### Claim 27 (depends on 25) The apparatus of claim 25, wherein the reconstruction unit further reduces the motion artifacts reduced by the pre-processing unit. ### Claim 28 (depends on 25) The apparatus of claim 25, wherein pre-processing by the pre-processing unit includes down-sampling the heart-related signal to produce a down-sampled heart-related signal, the down-sampling being at a sampling rate less than an original sampling rate. ### Claim 29 (depends on 28) The apparatus of claim 28 wherein: the time-varying spectral analysis is based on a frequency resolution; and the down-sampling affects the frequency resolution of the time-varying spectral analysis. ### Claim 30 (depends on 28) The apparatus of claim 28, wherein the pre-processing unit is further configured to compute a derivative of the down-sampled heart-related signal to reduce the motion artifacts. ### Claim 31 (depends on 30) The apparatus of claim 30, wherein the pre-processing unit is further configured to compute an absolute value of the derivative to further reduce the motion artifacts. ### Claim 32 (depends on 25) The apparatus of claim 25, wherein the reconstruction unit is further configured to perform the time-varying spectral analysis by computing a time-frequency spectrum (TFS) of the pre-processed heart-related signal. ### Claim 33 (depends on 32) The apparatus of claim 32, wherein the TFS computed is a 3-dimensional spectra including a time-varying amplitude or power distribution with respect to time and frequency. ### Claim 34 (depends on 32) The apparatus of claim 32, wherein the TFS computed is a time-varying power spectral density (PSD). ### Claim 35 (depends on 32) The apparatus of claim 32, wherein the reconstruction unit is further configured to limit the TFS computed to a given frequency range. ### Claim 36 (depends on 35) The apparatus of claim 35, wherein the given frequency range is 0.5 Hz to 3 Hz. ### Claim 37 (depends on 32) The apparatus of claim 32, wherein: the TFS is computed for each shift of a windowed data segment of the pre-processed heart-related signal; and the reconstruction unit is further configured to reconstruct the heart related signal for each shift of the windowed data segment. ### Claim 38 (depends on 37) The apparatus of claim 37, wherein, at each shift of the windowed data segment subsequent to an initial windowed data segment, the reconstruction unit reconstructs the representation by: retaining up to a pre-determined number of frequency spectra to produce a subset of frequency spectra; and selecting a frequency component to produce a selected frequency component for the reconstructing, the selected frequency component selected from amongst frequency components of the subset of frequency spectra and a previous frequency component, the previous frequency component having been selected for a previous shift of the windowed data segment to reconstruct the heart-related signal for the previous shift. ### Claim 39 (depends on 25) The apparatus of claim 25, wherein the time-varying spectral analysis is a first time-varying spectral analysis and wherein the reconstruction unit is further configured to perform the reconstructing based on a second time-varying spectral analysis of a motion signal, the motion signal output by a motion sensor and representative of the motion artifacts in the heart-related signal. ### Claim 40 (depends on 39) The apparatus of claim 39, wherein the reconstruction unit is further configured to employ the second time-varying spectral analysis of the motion signal to produce a movement classification of the movement, and wherein the reconstructing is further based on the classification of the movement. ### Claim 41 (depends on 39) The apparatus of claim 39, wherein the heart-related signal and the motion signal are output by the biomedical sensor and the motion sensor, respectively, concurrently. ### Claim 42 (depends on 39) The apparatus of claim 39, wherein the apparatus includes the biomedical sensor and the motion sensor. ### Claim 43 (depends on 39) The apparatus of claim 39, wherein the motion sensor is an accelerometer. ### Claim 44 (depends on 25) The apparatus of claim 25, further comprising a heart rate unit configured to employ the reconstructed representation to determine a heart rate estimate. ### Claim 45 (depends on 25) The apparatus of claim 25, further comprising a heart rate variability (HRV) unit configured to employ the reconstructed representation to determine a heart rate variability (HRV) estimate. ### Claim 46 (depends on 25) The apparatus of claim 25, further comprising an ailment unit configured to employ the reconstructed representation to detect or predict a heart-related ailment, the heart-related ailment including at least one of a heart rate variability (HRV) condition, atrial fibrillation condition, congestive heart failure condition, and tachycardia condition. ### Claim 47 (depends on 25) The apparatus of claim 25, wherein the reconstruction unit, the output unit, and the pre-processing unit are configured to reconstruct, pre-process, and output, respectively, in real-time with respect to outputting of the heart-related signal by the biomedical sensor. ### Claim 48 (depends on 25) The apparatus of claim 25, wherein the reconstruction unit, the output unit, and the pre-processing unit are configured to reconstruct, pre-process, and output, respectively, in non-real-time with respect to outputting of the heart-related signal by the biomedical sensor. ### Claim 49 A non-transitory computer-readable medium having encoded thereon a sequence of instructions which, when loaded and executed by a processor, causes the processor to reconstruct a heart-related signal output by a biomedical sensor, the processor reconstructing the heart-related signal by: pre-processing the heart-related signal to produce a pre-processed heart-related signal; reconstructing a representation of the heart-related signal to produce a reconstructed representation of the heart-related signal, the reconstructing based on a time-varying spectral analysis of the pre-processed heart-related signal, the heart-related signal including motion artifacts, the motion artifacts being signal artifacts produced by movement of the biomedical sensor relative to a sensing location, the pre-processing reducing the motion artifacts in the pre-processed heart-related signal for the reconstructing, the heart-related signal being an electrocardiogram (ECG) signal; and outputting the reconstructed representation of the heart-related signal.