Seismocardiograms return valid heart rate variability indices

HRV indices have traditionally been acquired using interbeat intervals obtained from the electrocardiogram (ECG) R-wave. Preliminary studies have recently shown, however, that interbeat intervals obtained from seismocardiogram (SCG) isovolumic moment point return some valid HRV measurements. This presents an interesting discovery due to the recent ubiquity of affordable accelerometers of satisfactory sensitivity in mobile phones. For this purpose an orthostatic stress test of graded lower body negative pressure (LBNP) was used to compare HR V indices obtained from ECG and SCG during periods of different orthostatic stress. We conclude that estimates of interbeat intervals obtained using SCG markers are valid measurements of interbeat interval when compared with ECG and lend themselves validly to time-domain and frequency-domain HRV analysis. It is our recommendation that aortic opening SCG markers be used to obtain interbeat intervals as they represent well defined events and are obtainable without the use of ECG markers.