Table 1: The definitions of heart rate variability parameters.
|
Variable |
Unit |
Description |
|
Time domain analysis |
||
|
SDNN |
ms |
Standard deviation of all NN intervals (normal to normal) |
|
RMSSD |
ms |
The square root of the mean of the sum of the squares of differences between adjacent NN intervals |
|
pNN50 |
% |
Percentage of successive NN intervals that differ by more than 50 ms |
|
Frequency domain analysis |
||
|
TOTAL power |
ms2 |
Variance of all NN intervals (≤ 0.4 Hz) |
|
VLF |
ms2 |
Power in very low frequency range (≤ 0.04 Hz) |
|
LF |
ms2 |
Power in low frequency range (0.04-0.15 Hz) |
|
HF |
ms2 |
Power in high frequency range (0.15-0.4 Hz) |
|
LF/HF |
|
Ratio LF/HF |