Table 4. HRV characteristics in evening wake according to OSA severity and MACCE.
| Controls n = 15 |
AHI <20 n = 36 |
AHI ≥20 n = 32 |
No MACCE n = 49 |
MACCE n = 19 |
|
|---|---|---|---|---|---|
| HR, 1/min | 63 (55–77) | 67 (58–80) | 66 (58–78) | 67 (58–78) | 67 (58–82) |
| NNI Min, ms | 778 (111) | 752 (117) | 772 (105) | 771 (105) | 736 (125) |
| NNI Max, ms | 1095 (173) | 1028 (169) | 1041 (169) | 1032 (165) | 1038 (178) |
| NNI Mean, ms | 956 (158) | 899 (129) | 905 (132) | 902 (131) | 901 (127) |
| NNI Dev, ms | 44 [18] | 34 [30] | 34 [19] | 33 [21] | 36 [31] |
| NNI RMSSD, ms | 23 [14] | 22 [15] | 22 [18] | 21 [13] | 24 [32] |
| NNI pNN50, % | 2.8 [4.5] | 1.5 [3.8] | 3.0 [5.8] | 1.5 [4.4] | 2.5 [7.5] |
| NNI SampEn | 1.2 (0.2) | 1.3 (0.3) | 1.3 (0.3) | 1.3 (0.3) | 1.2 (0.3) |
| NNIS Total, ms2 | 1541 [1159] | 803 [2148] | 1067 [1129] | 910 [1420] | 1012 [2561] |
| NNIS ULF, ms2 | 179 [155] | 54 [287] | 62 [145] | 53 [188] | 85 [255] |
| NNIS VLF, ms2 | 1108 [1000] | 414 [98] | 438 [710] | 424 [825] | 427 [816] |
| NNIS LF, ms2 | 463 [518] | 247 [341] | 186 [299] * | 227 [328] | 180 [651] |
| NNIS HF, ms2 | 104 [128] | 63 [154] | 84 [145] | 72 [128] | 91 [356] |
| NNIS LF/HF | 5.3 [6.3] | 3.2 [4.3] | 2.0 [3.6] * | 2.6 [3.4] | 2.2 [3.9] |
| NNIS nLF, nu | 81 (10) | 70 (18) | 63 (20) † | 69 (17) | 60 (24) † |
| NNIS nHF, nu | 18 (9) | 27 (15) | 33 (18) † | 28 (15) | 35 (21) † |
| NNI Alpha 1 | 1.37 (0.21) | 1.16 (0.32) * | 1.11 (0.33) * | 1.15 (0.30) * | 1.08 (0.39) * |
Data are mean (standard deviation) or median [interquartile range] except for mean (range) for heart rate (HR). AHI = Apnea-hypopnea index, Alpha 1 = Fractal scaling exponent alpha 1, Dev = Standard deviation of NNI, HF = Power in the high frequency range (0.15–0.4 Hz), LF = Power in low frequency range 0.04–0.15 Hz), MACCE = Major adverse cardiovascular and cerebrovascular event, ms = millisecond, nHF = normalized HF ratio, nLF = normalized LF ratio, NNI = normal-to-normal interval (i.e. time between normal beats in the electrocardiogram), NNIS = NNI spectrum, pNN50 = Proportion of NNI >50 ms, RMSSD = Root mean square of the sum of successive differences (between adjacent normal-to-normal intervals, i.e. beat-to-beat variability), SampEn = Sample entropy, Total = Total power of the NNI spectrum (i.e. overall autonomic activity), ULF = Power in the ultra-low frequency range (≤0.003 Hz), VLF = Power in the very low frequency range (0.003–0.04 Hz).
*: p <0.05 vs. controls
†: p <0.01 vs. controls. One-way analysis of variance with Dunnett’s post hoc was used to test for differences between each patient group (with and without OSA/MACCE) vs. controls. Analysis of covariance was used to test for independent differences between patient groups (with vs. without OSA/MACCE). Non-normally distributed variables were log-transformed (natural logarithm) before the statistical analyses (non-transformed values with IQRs in square brackets shown in tables).