The frequency domain contains the low frequency (LF) band (0.04–0.15 Hz), reflecting the sympathetic tone in contrast to the vagal tone effect on cardiac function it also has the high frequency (HF) band (0.15–0.4 Hz), which reflects the vagal tone variability associated with the respiratory cycle and with changes in blood pressure and this domain also takes in the LF/HF ratio, representing the absolute and relative changes between the sympathetic and parasympathetic tones ( 37). The time domain includes the standard deviation of the normal-to-normal intervals (hereinafter SDNN) over the entire recording period in ms, representing the sympathetic and parasympathetic activity, without distinguishing between pronounced sympathetic activity and vagal tone withdrawal it also includes the difference between consecutive R-wave-to-R-wave (R–R) intervals, which includes the percentage of successive R–R intervals >50 ms (hereinafter pNN50) and it includes the root-mean-square of successive R–R interval differences (hereinafter rMSSD) in ms representing parasympathetic activity ( 5). HRV may be evaluated through the time and frequency domains (TFD). Several studies have assessed its modulation through HRV analyses in dogs with different pathologies such as mitral valve degeneration, sick sinus syndrome, epilepsy, upper airway obstruction, or diabetes ( 4, 15, 20, 21, 22, 24, 36). The ANS plays an important role in the regulation of physiological and patho-physiological processes. This is a practicable and non-invasive method for measuring ANS balance and has been proven to be simple and effective ( 37). Heart-rate variability (HRV) represents the oscillations in interval between successive normal heart beats as a result of autonomic nervous system (ANS) activity ( 5).
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |