An investigation on autonomic effects by using PR intervals

Abstract

Many experts investigated the relations between the heart and the automatic nervous system (ANS). Most commonly, physicians nowadays use the heart rate variability (HRV) to observe ANS more than others.Instead of previous HRV method [3], the aim of this research is to find additional ANS indicator (s) IntroductionThe heart is innervated by both divisions of the autonomic nervous system (ANS), which can modify the rate of the contraction, even though nervous stimulation is not required to initiate contraction [1]. Many experts are looking for the relations between the heart and the automatic nervous system (ANS). Most commonly, physicians nowadays use the heart rate variability (HRV) to observe ANS more than others. Heart rate variability, derived from the electrocardiogram (ECG), is a measurement of these naturally occurring, beat-to-beat changes in heart rate.However, the PR interval represents the atrioventricular conduction time (AVCT), and the AVCT is coupled to the sympathetic / parasympathetic activities of the ANS [8]. Hence, the importance of PR-interval studies offers a better knowledge of the neural activity in the field of pacemaker's design and ANS study. Unfortunately, little is known about the PR autonomic modulations and the problem of estimation has been rarely addressed [2][3]. The major reason, according to HRV guidelines [3], is that precise location of a P wave fiducial point is very hard to achieve in surface ECGs.In order to overcome the problem, a method is provided to obtain a location of a P-wave fractal point in surface ECGs recorded with the current technology. In addition, the research investigated PR interval analysis and compared with ordinary HRV analysis by applying the same 90 o head-up tilt experiment.In general, the frequency response of HRV is divided into three standard segments: high frequency (HF -about 0.25 Hz), low frequency (LF -about 0.1 Hz), and very low frequency (VLF -0.04Hz to 0.13 Hz). Malik et al. [3] indicated that the ratio of LF and HF power changes when subjects moved from resting to 90° head-up tilt position. Our aim is mainly observe PR interval variability and search for significance on ANS regulation mechanism. Methodology P, Q, R, S, and T point detectionSeveral digital signal processing technologies were utilized on raw ECG signals to detect PQRST fiducial points, including digital filtering, Pan and Tompkins method, first derivative ECG method (i.e., dECG) [9], and the zero-crossing method. After those steps, fiducial points are correctly detected and several interested ECG features, such as RR, PR, and PP intervals, may be able to investigate.In order to accomplish ECG analysis, such as HRV and PR analysis, it is obvious that the R point is the major landmark which needs to be detected first. After digital filtering [4], a reliable, real-time QRS detection algorithm [5] is essential to apply. Pan and Tompkins method [5] was used in this research to determine all the R points in order to calculate R-R intervals.Once the R point is found, the...

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