PP.32.26

Abstract

Objective: Seismocardiogram (SCG) is the measure of the minute vibrations produced by the beating heart and the blood ejection from the ventricle into the vascular tree. It can be detected by placing an accelerometer on the sternum of the individual under evaluation. This signal reflects mechanical events of the heart contraction, including the opening and closure of mitral and aortic valves, and hemodynamic events such as the point of maximal blood flow acceleration in the aorta. Recently we demonstrated that SCG, one ECG lead and respiration can be easily detected out of the laboratory setting by a textile-based wearable system (the MagIC system). Aim of this pilot study was to verify the feasibility of a beat-to-beat estimation of cardiac mechanical features from the joint ECG and SCG assessment during sleep. Design and method: A 24-h signal recording was performed by the MagIC system in one healthy subject. Two sleep data segments (each lasting 30 min, for a total of 2978 heart beats) were considered for the study and the following parameters were derived on a beat-to-beat basis: RR interval (RRI), Pre-Ejection Period (PEP), Isovolumic Contraction Time (ICT), Left Ventricular Ejection Time (LVET), Isovolumic Relaxation Time (IRT). Results: Data analysis showed that more than 80% of the data segments could be used for the beat-to-beat estimation of the above parameters. Their average beat-to-beat means ± standard deviation were: RRI 1079 ± 45.6ms, PEP 102 ± 7.1ms, ICT 46 ± 8.3ms, LVET 319 ± 11.1, IRT 54 ± 7.9ms. Additionally, spectral analysis indicated that 1) respiration largely influences the dynamics of most of the parameters (25 ms for PEP, 20 ms for ICT, 35 for LVET, no effect on IRT); 2) variability of cardiac intervals is only marginally influenced by the RRI variability; 3) appreciable spectral power at frequencies < or = 0.1 is only observed in the RRI spectrum and not in the spectra of the other indexes. Conclusions: These findings represent the very first description of the beat-to-beat variability of cardiac mechanical indexes, obtained through wearable sensors. Further investigations in a suitable sample of subjects are in progress to confirm the present results.