Accurate and consistent automatic seismocardiogram annotation without concurrent ECG

Seismocardiography (SCG) is the measurement of vibrations in the sternum caused by the beating of the heart. Precise cardiac mechanical timings that can only be obtained from SCG are critically dependent on accurate identification offiducial points. So far, SCG annotation has relied on concurrent ECG measurements. We have designed an algorithm capable of annotating SCG without the use any other concurrent measurement. We subjected 18 participants to graded lower body negative pressure. We collected ECG and SCG, obtained R peaksfrom the former, and annotated the latter by hand, using these identified peaks. We also annotated the SCG automatically. We compared the isovolumic moment timings obtained by hand to those obtained using our algorithm. Mean accuracies for increasing levels of negative pressure were 97.61 ± 3.39%, 93.32 ± 5.33%, 78.28 ± 14.29%, 58.68 ± 17.58%, and 63.36 ±14.23%. We also compared LF/HF ratios obtained from isovolumic moments to those obtained from R peaks. For indices obtainedfrom automatic annotations, the mean differences were 0.16±0.19, -0.10±0.58, 0.89±0.85, -1.22±0.62, and 2.30 ± 1.10 for increasing levels of negative pressure.