Table 1.
HRV indices based on IBI intervals.
| Parameter | Unit | Description |
|---|---|---|
| SDNN | ms | Standard deviation of NN intervals a |
| RMSSD | ms | Root mean square of successive RR intervals differences |
| TRI | Integral of the density of the RR interval histogram divided by its height | |
| TINN | ms | Baseline width of the RR interval histogram |
| ApEn | Approximate entropy, which measures the regularity and complexity of a time series | |
| SD1 | ms | Poincaré plot standard deviation perpendicular to the line of identity |
| SD2 | ms | Poincaré plot standard deviation along the line of identity |
| SD1/SD2 | Ratio of SD1-to-SD2 | |
| HR | bpm | Heart Rate |
| VLF | ms2 | Power in VLF range (<0.04 Hz) |
| LF | ms2 | Power in LF range (0.04–0.15 Hz) |
| HF | ms2 | Power in HF range (0.15–0.4 Hz) |
| pLF | LF power in normalized units | |
| pHF | HF power in normalized units | |
| LF/HF | Ratio LF (ms2)/HF (ms2) |
a NN intervals: interbeat intervals from which artifacts have been removed.