Multi-Scale Fractal Dimension to Quantify Heart Rate Variability and Systolic Blood Pressure Variability: A Postural Stress Analysis

Abstract

This paper presents multi-scale fractal dimension (MFD) for the complexity assessment of heart rate variability (HRV) and systolic blood pressure variability (SBPV) under postural stress. A comparison of MFD with multi-scale approximate entropy (MAE) at multiple time scales ([Formula: see text]–10) is presented. The simulations were conducted on 50 random noise (RN), fractional Brownian motion (fBm), and MIX(p) [ 1 ] series along with standard EuroBaVar dataset. Also, 50 healthy volunteers, 20 post-acute myocardial infarction (AMI) patients participated in the study. It is observed that MFD and MAE decrease with [Formula: see text] for healthy volunteers and remained constant for post AMI and BRS failure patients. Average MFD of HRV in supine position is always significantly different than standing position scale except [Formula: see text], whereas the average MAE of HRV shows no significant difference ([Formula: see text]) between supine and standing postures at each [Formula: see text] except [Formula: see text] for healthy volunteers. Average MFD of HRV in supine position is significantly different than the standing position for [Formula: see text]–7, whereas the average MAE of HRV shows significant difference ([Formula: see text]) between supine and standing postures at [Formula: see text] for post AMI, and patients with impaired baroreflex sensitivity (BRS). Average MFD of SBPV in position is significantly different ([Formula: see text]) than standing position at each [Formula: see text], whereas the average MAE of SBPV shows no significant difference ([Formula: see text]) between supine and standing postures at each [Formula: see text] except [Formula: see text]. The complexity of HRV in standing position is less than that of supine position as shown by lower MFD and MAE values in standing than that of supine position, however, the complexity of SBPV decreases from standing to supine position indicating prevalence of sympathetic control.