Utilizing Gyroscopes Towards the Automatic Annotation of Seismocardiograms

This paper reports on the use of the rotational component of chest vibrations for the automatic annotation of seismogram (SCG) recordings for the first time. An inertial measurement unit consisting of a three-axis MEMS accelerometer and a three-axis MEMS gyroscope is used for recording chest vibrations. The gyroscope signal acts as a reference for the detection of the isovolumic moment (IM) and aortic valve closure (AC) peaks on the SCG signal. Experimental results from ten subjects at rest indicate a close correlation between the timings of the P1 and P2 peaks of the gyroscope energy waveform and the accelerometer IM and AC peaks, and provide the capability for ECG-free annotation of the SCG signal using the energy peaks, which are simpler to detect. Furthermore, extended experiments from walking subjects reveal the feasibility of using the head-to-foot axis gyroscope recordings as an enhancement tool for the annotation of the SCG signal.