Variation of Seismocardiogram-Derived Cardiac Time Intervals and Heart Rate Variability Metrics Across the Sternum

Abstract

Cardiac time intervals (CTIs) are vital indicators of cardiac health and can be noninvasively assessed using a combination of electrocardiography (ECG) and seismocardiography (SCG), a method of capturing cardiac-induced chest vibrations via accelerometers. This study investigates the impact of accelerometer placement along the sternum on SCG-derived CTI estimations and heart rate variability (HRV) parameters. A semiautomated algorithm was developed to detect SCG fiducial points and seven CTIs from thirteen healthy individuals. Comparative analysis with manually selected peaks and gold-standard ECG was conducted to assess fiducial point detection accuracy. Results indicate the highest recall and precision in aortic valve opening (0.84-1.00 and 0.96-1.00, respectively) and mitral valve closure (0.77-1.00 and 0.93-1.00, respectively) detection. Aortic valve closure (0.43-1.00 and 0.61-1.00, respectively) and mitral valve opening (0.64-1.00 and 0.91-1.00, respectively) detection, although slightly less accurate due to signal intensity variations, demonstrated overall effectiveness compared to manually selected peaks. Furthermore, SCG-derived heart rates showed a high correlation coefficient (r > 0.9) with the gold-standard ECG heart rates. Single-factor ANOVA revealed significant differences (p < 0.05) in SCG-derived CTI estimations based on sensor locations on the sternum, highlighting the importance of sensor placement for accurate assessments. Future research will focus on optimizing sensor placement based on gold-standard imaging such as echocardiography to evaluate the best chest locations for accurate CTI estimations.