Feasibility of 24-Hour Monitoring and Circadian Analysis of the Cardiac Electro-Mechanical Activity Using Wearable Inertial Sensors

This study investigates the application of wearable technology for continuous monitoring of cardiac electromechanical activity in real-world scenarios, utilizing ECG and seismocardiographic (SCG) signals acquired for 24 hours through inertial sensors. In 22 healthy volunteers, a single-channel ECG (fs = 1024 Hz) and SCG (triaxial accelerometer and gyroscope, fs = 64 Hz) signals were simultaneously recorded using a wearable device. Based on the ECG, the quality of the SCG for each cardiac beat was analysed and heartbeats were labelled to exclude artefacts, and to allow detection of cardiac mechanical events, such as isovolumetric contraction, aortic valve opening and closure, from which left ventricular ejection time (LVET) and other contractility-related SCG parameters were derived. Lastly, the circadianity of the computed parameters was evaluated. High feasibility of SCG beats detection was reached during the night-time (82[69.9;90.1]%) compared to the day (49.9 [40;52]%). The presence of circadian patterns in both morphological and temporal SCG-derived parameters was for the first time evaluated and confirmed, thus enhancing the capabilities of a commercially available device typically used for postural analysis. Day-night differences could serve as reference ranges for comparison with future patient data.