Table 1 Overview of the HRV parameters
Parameter | Unit | Description |
|---|---|---|
Time-domain measures | ||
Mean HR | bpm | Mean heart rate (reflects physical activity and sympatho-vagal balance) |
Mean RR | ms | Mean of the selected beat-to-beat RR interval series (inversely proportional to mean HR) |
SDNN | ms | Standard deviation of the IBI of normal sinus beats (demonstrates overall HRV) |
HRVindex | ms | Integral of the density of the RR interval histogram divided by its height |
SDANN | ms | Standard deviation of the averages NN (normal-to-normal) intervals for each of the 5 min segments during a 24 h recording |
RMSSD | ms | Root mean square of successive RR interval differences (reflects mainly parasympathetic activation of the autonomic nervous system) |
pNN50 | % | Percentage of successive NN intervals that differ by more than 50 ms (NN50) divided by the total number of all NN intervals |
Frequency-domain measures | ||
HRV | ms2 | Total energy across all spectral bands of the frequency analysis |
LF power | ms2 | Absolute power of the low-frequency band (frequency range 0.04–0.15 Hz) (reflects both sympathetic and parasympathetic activation) |
HF power | ms2 | Absolute power of the high-frequency band (frequency range 0.15–0.4 Hz) (reflects parasympathetic activation) |
LF/HF | – | LF/HF power ratio (estimates sympatho-vagal balance) |
Non-linear measures | ||
SD1 | ms | Poincaré plot standard deviation perpendicular the line of identity |
SD2 | ms | Poincaré plot standard deviation along the line of identity |