Heart Rate Variability Analysis on Forcecardiography Signals: A Preliminary Study

Forcecardiography (FCG) is a novel, non-invasive, cardio-mechanical monitoring technique that has been recently proposed to simultaneously monitor respiration, infrasonic cardiac vibrations and heart sounds via force sensors placed on the subjects’ chests. Heart Rate Variability (HRV) analysis is a wellknown method to reveal autonomic nervous control and, usually, it is obtained by processing the Electrocardiogram (ECG). This study aims to assess the feasibility of the sole FCG signal in providing reliable HRV indices. ECG and FCG signals were simultaneously recorded from seven healthy subjects. ECG and FCG signal were independently processed to identify every single heartbeat and the inter-beat intervals were computed. Then, typical time-domain, frequency-domain and non-linear HRV indices were extracted using FCG inter-beat intervals and compared with their correspondent ECG indices, held as reference. Very little difference between ECG and FCG inter-beat intervals measurement were found. The limits of agreement of the two measurements resulted [−4.0, 4.2] ms, which represent negligible errors in clinical application. The statistical comparison between the ECG and FCG-derived HRV indexes reported high correlations (in excess of 0.9) and narrow limits of agreement between measurements for all the considered indexes. These preliminary results demonstrated the capability of FCG in providing reliable cardiac inter-beat intervals and HRV indices. Therefore, FCG could offer a valid alternative to ECG in heart rate monitoring via a standalone cardio-mechanical approach.