Table 1.
Selected time- and frequency-domain measures of HRV.
| Variable | Units | Description: time-domain measures |
|---|---|---|
| SDNN | ms | Standard deviation of all NN intervals |
| RMSSD | ms | The square root of the mean squared difference between adjacent NN intervals |
| Variable | Units | Description: frequency-domain measures |
| TP | ms2 | Variance of all NN intervals over the temporal segment |
| LF/HF | Ratio LF [ms2]/HF [ms2] | |
| LFnu | n.u. | LF power in normalized units LF/(TP-VLF) × 100 |
| HFnu | n.u. | HF power in normalized units HF/(TP-VLF) × 100 |
According to the Task Force of The European Society of Cardiology and The North American Society of Pacing and Electrophysiology (Camm etal., 1996). TP, total power; LF, low frequency; HF, high frequency; ms, miliseconds; n.u., normalized units.