Table 3.
Time and frequency domain parameters of short-term heart rate variability in probable MSA subgroups and healthy controls
| Short-term heart rate variability | MSA-P (n1=22) | MSA-C (n2=23) | Controls (n3=45) | Test statistic | P |
|---|---|---|---|---|---|
| Time domain parameters | |||||
| SDNN (ms)$ | 14.09 (8.54) | 16.59 (13.03) | 41.26 (17.36) | 55.42 | <0.001*** |
| RMSSD (ms)$ | 8.7 (9.12) | 11.9 (10.07) | 30.29 (18.12) | 44.41 | <0.001*** |
| NN50 (count)$ | 0.001 (2) | 0.001 (1) | 26 (60) | 46.64 | <0.001*** |
| pNN50 (%)$ | 0.001 (0.58) | 0.001 (0.29) | 8.53 (15.05) | 44.07 | <0.001*** |
| Average HR# | 82.67±14.48 | 77.7±12.14 | 68±11.18 | 10.26 | <0.001*** |
| Frequency domain parameters | |||||
| Total power (ms2)$ | 183.78 (250) | 255.61 (384.1) | 1639.74 (1500) | 55.53 | <0.001*** |
| HF power (ms2)$ | 26.03 (38.7) | 29.67 (123.93) | 352.23 (496.9) | 47.89 | <0.001*** |
| LF power (ms2)$ | 26.59 (46.77) | 48.49 (79.72) | 421.28 (390) | 54.75 | <0.001*** |
| LF/HF ratio$ | 1.25 (1.53) | 1.76 (2.44) | 0.87 (0.88) | 4.31 | 0.116 |
MSA=multiple system atrophy; MSA-P=parkinsonian variant; MSA-C=cerebellar variant; SDNN=standard deviation of RR Intervals; RMSSD=square root of the mean of the sum of squares of differences between adjacent RR intervals; NN50=count of number of pairs of RR intervals differing by >50 ms; pNN50 (%) = percentage of count of number of pairs of adjacent RR intervals differing by more than 50 ms; average HR=average heart rate; HF power=high-frequency power; LF power=low-frequency power; LF/HF ratio=sympathovagal balance; IQR=interquartile range. #One way analysis of variance, values expressed as Mean±SD. $Kruskal-Wallis test, values expressed as median (IQR). ***P<0.001