What is HRV?

A.What is HRV(Heart Rate Variability)
Analysis of Heart Rate Variability, HRV, has become a mainstream study in the recent decade. After Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology determined the standard of Analysis of Heart rate Variability in 1996, the relative parameter (LF, HF, LF%, HF%, and LF/HF) of autonomic nervous function can be obtained from the spectral analysis, and the development of it can be applied to various departments, such as: diabetes(Gottsater, Ahlgren, Taimour & Sundkvist,2006; Sun, Yang & Kuo, 2006; Flynn, Jelinek & Smith, 2005), cardiovascular disease(Evrengul, Tanriverdi, Kose, Amasyali, Kilic, Celik & Turhan, 2006; Kuo & Yang, 2002), and dyssomnia(Yang, Lai, Lai & Kuo, 2002; Kuo & Yang, 2004; Irwin, Valladares, Motivala, Thayer & Ehlers, 2006). Kuo, Lin, Yang, Li, Chen and Chou(1999) has well established that autonomic nervous relate to multiple disease, especially cardiovascular disease, by the study of the differences of the autonomic nervous between gender and age.

B、What isFrequency-domain analysis?
Of the different methods of measuring HRV, frequency-domain analysis has a greater ability to differentiate vagal and sympathetic modulation of heart rate than do time-domain methods (Spallone and Menzinger, 1997). It has now become a sophisticated and noninvasive tool for detection of autonomic regulation of the heart. It has been well established that HRV can be categorized into high-frequency power (HF, 0.15-0.40 Hz) and low-frequency power (LF, 0.04-0.15 Hz) components according to its oscillating frequency and development mechanism (Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology., 1996). The HF component is equivalent to the respiratory sinus arrhythmia and is considered to present vagal control of heart rate (Fouad et al., 1984). The LF is jointly contributed by both sympathetic and vagal functions (Berger et al., 1989). The ratio of LF to HF (LF/HF) is considered to mirror sympathovagal balance or to reflect sympathetic modulations by some investigators (Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology., 1996; Malliani et al., 1991; Montano et al., 1994; Pagani et al., 1997). The definitions of all frequencies listed in Table 1 (Kuo et al., 2005).

C、What is SDNN(Standard deviation of the NN intervals)
SDNN represents for the standard variability between two hearts is about xx seconds. The SDNN of Heart rate variability can be considered as the indicator of whether a body is healthy or not.