Table 2 Explanation of HRV parameters by Time–Frequency-Domain and nonlinear Parameters (according to [19, 25])
HRV-parameter | Description | Activity as part of the autonomic nervous system | Reaction with increased stress |
|---|---|---|---|
Time-domain | |||
Mean HR (1/min) | The mean heart rate | Sympathetic and parasympathetic nervous system (SNS and PNS) | ↑ |
STD HR (1/min) | Standard deviation of instantaneous heart rate values | ||
Mean RR or NN (ms) | The mean of RR intervals | Unclear classification | ↓ |
SDNN (ms) | Standard deviation of RR intervals | SNS and PNS | ↓ |
RMSSD (ms) | Square root of the mean squared differences between successive RR intervals | PNS | ↓ |
NN50 | Number of successive RR interval pairs that differ more than 50 ms | PNS | ↓ |
pNN50 (%) | NN50 divided by the total number of RR intervals | PNS | ↓ |
RR_Tri | The integral of the RR interval histogram divided by the height of the histogram | Unclear classification | |
TINN (ms) | Baseline with of the RR interval histogram | Unclear classification | ↓ |
Frequency-domain (FFT) | |||
FFT VLF-peak (Hz) | VLF band peak frequencies | Unclear classification | No information |
FFT LF-peak (Hz) | LF band peak frequencies | Unclear classification | No information |
FFT HF-peak (Hz) | HF band peak frequencies | Unclear classification | No information |
FFT_VLF_po (ms2) | Absolute powers of VLF bands | SNS | ↑ |
FFT_LF_po (ms2) | Absolute powers of LF bands | SNS and PNS | ↑ |
FFT_HF_po (ms2) | Absolute powers of HF bands | PNS | ↓ |
FFT TP (ms2) | Total Power: Overall Power spectral density: from 0.00001 to 0.4 Hz | Unclear classification | ↓ |
FFT_LF_po% (%) | Relative power of LF bands | SNS and PNS | ↑ |
FFT_HF_po% (%) | Relative power of HF bands | PNS | ↓ |
FFT LF nu | Low frequency normalized unit: LF/(Total Power-VLF) × 100 | SNS and PNS | ↑ |
FFT HF nu | High frequency normalized unit: HF/(Total Power − VLF) × 100 | PNS | ↓ |
FFT LF/HF | Ratio between LF and HF band powers | SNS and PNS | ↑ |
Nonlinear | |||
SD1 (ms) | The standard deviation of the Poincaré plot perpendicular to (SD1) and along (SD2) the line-of-identity | PNS | ↓ |
SD2 (ms) | The standard deviation of the Poincaré plot perpendicular to (SD1) and along (SD2) the line-of-identity | SNS and PNS | |
DFA1 | Detrended fluctuation analysis: Short term fluctuation slope | Unclear classification | |
DFA2 | Detrended fluctuation analysis: Long term fluctuation slope | Unclear classification | |