Parameter | Units | Description |
---|---|---|
Time-domain | ||
\(\stackrel{-}{\mathrm{RR}}\) | [ms] | The mean of RR intervals |
 SDNN | [ms] | Standard deviation of normal to normal RR intervals |
\(\stackrel{-}{\mathrm{HR}}\) | [1/min] | The mean heart rate |
 SDHR | [1/min] | Standard deviation of instantaneous heart rate values |
 MinHR | [beats/min] | Min heart rate per minute |
 MaxHR | [beats/min] | Maximum heart rate per minute |
 RMSSD | [ms] | The root mean square of successive RR interval differences |
 NN50 | [count] | Number of successive RR interval pairs that differ more than 50 ms |
 pNN50 | [%] | NN50 divided by the total number of all NN intervals |
 HRV triangular index | – | The integral of the RR interval histogram divided by the height of the histogram |
 TINN | [ms] | Baseline width of the NN interval histogram |
Frequency-domain | ||
 VLF power | [ms2] | Absolute power of VLF band |
 LF power | [ms2] | Absolute power of LF band |
 HF power | [ms2] | Absolute power of HF band |
 LF/HF | – | Ratio between LF and HF band powers |
 Total power (TP) | [ms2] | Total spectral power |
 Normalized LFP | – | LF/(TP-VLF) |
 Normalized HFP | – | HF/(TP-VLF) |
Nonlinear | ||
 SD1 | [ms] | Poincaré plot standard deviation perpendicular the line of identity |
 SD2 | [ms] | Poincaré plot standard deviation along the line of identity |
 SD2/SD1 | [%] | Ratio of SD2 to SD1 |
 ApEn | – | Approximate entropy |
 SampEn | – | Sample entropy |
\({\alpha }_{1}\),\({\alpha }_{2}\) | – | Short-term and long-term fluctuations of detrended fluctuation analysis (DFA) |