Origin and significance of heart rate variability.

easurement of heart rate variability (HRV) has become an mportant research tool for both clinical and basic scientists 1,2). The better reproducibility and the possibility of easuring long-range heart rate (HR) fluctuations are dvantages of 24-h electrocardiographic (ECG) recordings ver short-term recordings in the assessment of HRV (2). ong-range oscillations of HR determine a larger proporion of 24-h HRV than do short-term oscillations. This henomenon can be demonstrated by plotting the (log) ower to (log) frequency of HRV in the region of ultraow-frequency (ULF) and very-low-frequency (VLF) power pectral bands, where an inverse power-law relationship (1/f ynamics) can be observed between the power and the