A comparison of heartbeat detectors for the seismocardiogram

The study aimed to study the accuracy in RR time series derived from the seismocardiogram when employing different heartbeat detectors in subjects measured in a quiet environment. The ECG and seismocardiogram of 17 healthy volunteers was recorded at a sampling frequency of 5 kHz using a Biopac acquisition system. The seismocardiogram was acquired using a triaxial accelerometer (LIS344ALH, ST Microelectronics). Four detectors of the heartbeat from the seismocardiogram were employed relying either on the Continuous Wavelet Transform or bandpass filtering. The detectors adapt their parameters to the morphology of the signal by estimating mean heart rate and the bandwidth of the signal associated to the heartbeat. For all detectors, the standard deviation of the error in the obtained RR time series is in mean slightly higher than 2 ms and the percentage of obtained RR time intervals that have an error higher than 30 ms is around 3.5%. The seismocardiogram, when measured in a quiet environment, can be used instead of the ECG to obtain reliable RR time series when using proper heartbeat detectors.Peer ReviewedPostprint (published version

A methodology to quantify the differences between alternative methods of heart rate variability measurement

This work proposes a systematic procedure to report the differences between heart rate variability time series obtained from alternative measurements reporting the spread and mean of the differences as well as the agreement between measuring procedures and quantifying how stationary, random and normal the differences between alternative measurements are. A description of the complete automatic procedure to obtain a differences time series (DTS) from two alternative methods, a proposal of a battery of statistical tests, and a set of statistical indicators to better describe the differences in RR interval estimation are also provided. Results show that the spread and agreement depend on the choice of alternative measurements and that the DTS cannot be considered generally as a white or as a normally distributed process. Nevertheless, in controlled measurements the DTS can be considered as a stationary process.Peer ReviewedPostprint (published version

Differences in QRS locations due to ECG lead: relationship with breathing

Results of heart rate variability analysis depend on the accuracy of the RR time series that is measured only in one lead of the ECG. RR time series can subtly change from lead to lead. We have obtained the ECG of 21 healthy subjects in a quiet measurement, sampled at 5 kHz and from the I and II standard leads. For each subject a total of 60 minutes was measured. The QRS complexes in both leads have been detected using a conventional QRS detector plus a further refinement using a matching template. Differences between the locations of the QRS complexes have been quantified and compared with the breathing signal of each subject as well as the derived RR time series. The typical uncertainty in the fiducial points and RR time series is usually below 1 ms and the errors are modulated by breathing.Peer ReviewedPostprint (published version

Differences in QRS locations due to ECG lead: relationship with breathing

Results of heart rate variability analysis depend on the accuracy of the RR time series that is measured only in one lead of the ECG. RR time series can subtly change from lead to lead. We have obtained the ECG of 21 healthy subjects in a quiet measurement, sampled at 5 kHz and from the I and II standard leads. For each subject a total of 60 minutes was measured. The QRS complexes in both leads have been detected using a conventional QRS detector plus a further refinement using a matching template. Differences between the locations of the QRS complexes have been quantified and compared with the breathing signal of each subject as well as the derived RR time series. The typical uncertainty in the fiducial points and RR time series is usually below 1 ms and the errors are modulated by breathing.Peer Reviewe

A comparison of heartbeat detectors for the seismocardiogram

The study aimed to study the accuracy in RR time series derived from the seismocardiogram when employing different heartbeat detectors in subjects measured in a quiet environment. The ECG and seismocardiogram of 17 healthy volunteers was recorded at a sampling frequency of 5 kHz using a Biopac acquisition system. The seismocardiogram was acquired using a triaxial accelerometer (LIS344ALH, ST Microelectronics). Four detectors of the heartbeat from the seismocardiogram were employed relying either on the Continuous Wavelet Transform or bandpass filtering. The detectors adapt their parameters to the morphology of the signal by estimating mean heart rate and the bandwidth of the signal associated to the heartbeat. For all detectors, the standard deviation of the error in the obtained RR time series is in mean slightly higher than 2 ms and the percentage of obtained RR time intervals that have an error higher than 30 ms is around 3.5%. The seismocardiogram, when measured in a quiet environment, can be used instead of the ECG to obtain reliable RR time series when using proper heartbeat detectors.Peer Reviewe

A methodology to quantify the differences between alternative methods of heart rate variability measurement

This work proposes a systematic procedure to report the differences between heart rate variability time series obtained from alternative measurements reporting the spread and mean of the differences as well as the agreement between measuring procedures and quantifying how stationary, random and normal the differences between alternative measurements are. A description of the complete automatic procedure to obtain a differences time series (DTS) from two alternative methods, a proposal of a battery of statistical tests, and a set of statistical indicators to better describe the differences in RR interval estimation are also provided. Results show that the spread and agreement depend on the choice of alternative measurements and that the DTS cannot be considered generally as a white or as a normally distributed process. Nevertheless, in controlled measurements the DTS can be considered as a stationary process.Peer Reviewe