Table 2.
Most used HRV measures. (modified from Heart Rate Variability: Standards of Measurement, Physiological Interpretation, and Clinical Use. Task Force of the European Society of Cardiology the North American Society of Pacing Electrophysiology. Circulation. 1996;93:1043–1065).
| Time domain indexes | SDNN | Standard deviation of all NN intervals |
| SDANN | Standard deviation of the averages of NN intervals in all 5-minute segments of the entire recording | |
| RMSSD | The square root of the mean of the sum of the squares of differences between adjacent NN intervals | |
| SDNN index | Mean of the standard deviations of all NN intervals for all 5-minute segments of the entire recording | |
| pNN50 | NN50 count divided by the total number of all NN intervals | |
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| Frequecy domain indexes | Total power | Variance of all NN intervals (≤0.4 Hz) |
| ULF | Power in the ULF range (≤0.003 Hz) | |
| VLF | Power in the VLF range (0.003–0.04 Hz) | |
| LF | Power in the LF range (0.04–0.15 Hz) | |
| HF | Power in the HF range (0.15–0.4 Hz) | |
| LF/HF | Ratio LF [ms2]/HF[ms2] | |