The Time Evolution of Frequency Components of Heart Rate Variability Using Wavelets

Abstract

The ruling action of the autonomic nervous system (ANS) controls is not static. Due to this dynamic action, the physiological parameters do not remain in the same stationary status but are modified by the evolving condition of the cardiovascular regulatory systems. Applications of conventional spectral approaches, such as Fourier transform (FT) or autoregressive (AR) model, to HRV analysis, thus, always remain problematic since they are applied based on the assumption of stationarity. Also capturing hidden dynamics in both healthy and chronically ill subjects could yield important insights into understanding physiological mechanisms. Heart rate variability analysis is complicated by the fact that these signals are typically both highly irregular and nonstationary i.e., their statistical character changes slowly or intermittently as a result of variations in background influences. FT and AR methods have served a critical role in the understanding of basal autonomic cardiac control. However, these algorithms have limitations in the study of heart rate for nonlinear variations and transient alterations. Here, the wavelet transform based heart rate variability analysis with emphasis on the time evolution of the different frequency components of HRV signal and sympathovagal balance has been shown to monitor ANS adaptations induced by physiological interventions like head up-tilt, forced breathing in the experimental protocol. The procedure was applied to quantify the time evolution of HRV parameters under steady state and to identify subperiods of steady-state during a sequence of physical activities. Results showed the capability of proposed techniques to provide additional practical diagnostic and prognostic insight by mapping autonomic abnormalities.

Indexing terms:

• ECG
• HRV
• Sympathovagal balance
• Wavelet transform
• Spectral Analysis

Additional information

Notes on contributors

Dilbag Singh

Dilbag Singh was born in Adyana (Panipat) in 1969. He received his BE (Electrical Engineering) from Punjab Engineering College, Chandigarh, India in 1991 and ME (Control & Guidance) from University of Roorkee in 1993. After a brief stint at Goodyear India Limited, Faridabad, he joined as Lecturer in Instrumentation and Control Engineering at National Institute of Technology, Jalandhar in 1994. Since 2005, he is Assistant Professor in the same department, where he is teaching UG/PG courses related to biomedical signal processing and instrumentation. He received his PhD in Electrical Engineering with the dissertation “Analysis and interpretation of heart rate and blood pressure variability” from Indian Institute of Technology Roorkee in 2004. His professional research activity lies in the field of biomedical signal processing, with main interest in signals of cardiovascular origin, time-frequency/time-scale signal analysis.

Vinod Kumar

Vinod Kumar obtained his BSc (Electrical Engineering) Hons degree from Punjab University in 1973, ME (Measurement & Instrumentation) Hons and PhD degree from University of Roorkee in 1975 and 1984 respectively. He joined the Electrical Engineering Department of University of Rookee (presently, IIT Roorkee) in 1975 and is presently Professor in Electrical Engineering Department of Indian Institute of Technology Roorkee.

He has guided 12 doctoral and more than 70 Master's theses and has more than 125 research publications in internationally reputed journals and Conference proceedings. He has undertaken large number of consultancy and sponsored projects from industries and government departments.

He holds membership of many professional bodies. He is a fellow of the Institute of Engineers (I), Institution of Electronics and Telecommunication Engineers and Biomedical Engineering Society of India. He is a Senior Member of IEEE, USA. He has many honors and awards to his credit, namely IETE K S Krishna Memorial Award, Khosla Cash A ward and Prize, Khosla Cash Prize, Khosla Annual Research Prize, Certificate of Merit for research papers by Institution of Engineers (I).

He has also conducted several courses, workshops for the benefit of faculty and field engineers. Dr Kumar served the institute as Associate Dean Academic, Director/Coordinator A VRC and Coordinator Information Super Highway Centre. He is presently Head, Continuing Education Centre. His areas of interest are measurement and instrumentation, medical instrumentation, medical image processing, digital signal processing and telemedicine.