ECG MONITORING SYSTEM FOR HEART RATE VARIABILITY ANALYSIS Marcel Stanciu, Daniela Faur , Anatolie Boev University Politehnica Bucharest, Faculty of Electrical Engineering, 313 Splaiul Independentei 0600042, +40214029258, +40213181610, smm93smm@yahoo.com, danielafaur@gmail.com Abstract -A method to analyse HRV (heart rate variability) using an ECG monitoring system is presented. Variations in heart rate may be evaluated by a number of methods. The current methodologies used to analyse HRV are based largely on linear techniques to analyse ‘past’ and ‘present’ electrocardiogram (ECG) data in time and frequency domains. For conventional time domain analysis, the variability in the R-R interval time series derived from an ECG recording is statistically summarised using conveniently calculated measures such as SDNN (standard deviation of time interval between consecutive R peaks) and RMSSD (root-mean square of the difference between two adjacent R-R intervals). Depending on the length of the analysed ECG recording, which may vary from a few minutes to 24 hours, and the choice of the time domain measure, both short-term and long-term HRV can be quantified and characterised. I. Introduction The autonomic nervous system (ANS) is the portion of the nervous system that controls the body’s visceral functions, including action of the heart, movement of the gastrointestinal tract and secretion by different glands, among many other vital activities. It is well known that mental and emotional states directly affect the ANS. Nowdays, research studies have examined the influence of emotions on the ANS utilizing the analysis of heart rate variability, which serves as a dynamic window into autonomic function and balance. This measure, derived from electrocardiogram (ECG), is a measurment of the naturally occuring beat to beat changes in the heart rate. Over the last 25 years, HRV analysis has established itself as a non-invasive research and clinical tool for indirectly investigating both cardiac and autonomic system function in both health and disease. This paper describes a measurement system for off line HRV analysis and introduces aspects regarding the design of an on line measurement system. II. Heart rate variability – Problem definition The last two decades have witnessed the recognition of a significant relationship between the autonomic nervous system and cardiovascular mortality, including sudden cardiac death. Experimental evidence for an association between a propensity for lethal arrhythmias and signs of either increased sympathetic or reduced vagal activity has encouraged the development of quantitative markers of autonomic activity [1]. ‘Heart Rate Variability’ has become the conventionally accepted term to describe variations of both instantaneous heart rate and RR intervals. In order to describe oscillation in consecutive cardiac cycles, other terms have been used in the literature, for example cycle length variability, heart period variability, RR variability and RR interval tachogram, and they more appropriately emphasize the fact that it is the interval between consecutive beats that is being analyzed rather than the heart rate per se. Stress, certain cardiac diseases, and other pathologic states affect on HRV. A good review of physiological origins and mechanisms of HRV can be found in [2]. The normal variability in heart rate is due to the synergistic action of the two branches of the ANS, which act in balance through neural, mechanical, humoral and other physiological mechanisms to maintain cardiovascular parameters in their optimal ranges and to permit appropriate reactions to changing external or internal conditions. In a healthy individual, thus, the heart rate estimated at any