5.3. Heart rate variability analysis (Studies III - IV)
Six patients with refractory TLE reported having experienced simple and/or complex partial seizures during the recording. Their HRV profile did not, however, show any particular pattern different from HRV profiles of the other patients and were, therefore, included in the analysis. None of the patients reported generalized seizures.The mean value of RR interval was similar in the patients and the control subjects. No significant arrhythmias were seen during ECG-recordings.
In Study III the values of SDNN (p < 0.05) and the spectral components VLF (p < 0.001), LF (p < 0.001) and HF (p < 0.001) were lower in patients with TLE compared to those of the control subjects. The slope of the power-law relationship of the HRV (p < 0.01) was deeper in the patient group than in the control subjects (Table 13).
The mean value of the ApEn (p < 0.05) of the refractory TLE patients was lower than that of the well controlled TLE, and the long term fractal correlation value α2 (p < 0.05) was smaller in patients with well controlled TLE. The values of the other HR measures among patients with refractory and well controlled TLE were similar (Table 13).
Altered HRV was not associated with any particular AED regimen, or the serum concentrations of different AEDs. Moreover, the duration of TLE did not correlate with the alterations of HRV.
Figures 5, 6 and 7 present examples of the power spectrum analyses of HRV, Poincaré plots and power-law relation slopes from a patient with TLE and from a healthy subject.
Table 13. Analysis of heart rate variation in patients with refractory and well controlled temporal lobe epilepsy and the control subjects.
| Measure | Patients with refractory TLE (n = 19) | Patients with well controlled TLE (n = 25) | All patients (n = 44) | Control subjects (n = 34) | p Value (Mann-Whitney) |
|---|---|---|---|---|---|
| RRI | 863 ± 103 | 819 ± 112 | 838 ± 109 | 850 ± 71 | 0.403 |
| SDNN | 154 ± 32 | 158 ± 51 | 156 ± 43 | 177 ± 44 | 0.039 |
| VLF | 1538 ± 762 | 1749 ± 1005 | 1658 ± 905 | 3256 ± 1765 | <0.001 |
| LF | 905 ± 472 | 1038 ± 507 | 981 ± 491 | 1901 ± 1308 | 0.001 |
| HF | 604 ± 502 | 628 ± 365 | 681 ± 424 | 1710 ± 2050 | 0.011 |
| ApEn | 0.93 ± 0.21† | 1.09 ± 0.32 | 1.02 ± 0.29 | 1.15 ± 0.21 | 0.045 |
| α1 | 1.22 ± 0.18 | 1.17 ± 0.18 | 1.19 ± 0.18 | 1.16 ± 0.1 | 0.292 |
| α2 | 1.03 ± 9.0 | 0.99 ± 7.64* | 1.01 ± 6.13 | 1.01 ± 6.13 | 0.824 |
| Slope of HRV | -1.32 ± 0.13 | -1.37 ± 0.21 | -1.35 ± 0.18 | -1.20 ± 0.21 | 0.002 |
| Values are mean (± SD); RRI, RR interval; SDNN, SD of all RRIs; VLF, very low frequency; LF, low frequency; HF, high frequency; SD1 instantaneous beat to beat RR interval variability; SD2, long-term continuous RR interval variability ApEn, approximate entropy; α2, long term scaling exponent; †, p = 0.021 compared to the patients with well controlled TLE; *, p = 0.037 compared to the patients with refractory TLE; **, p = all patients compared to the control subjects | |||||
In Study IV the values of SD (p < 0.001), SDNN (p <0.05), VLF (p < 0.001), LF (p < 0.001), HF (p < 0.05), SD1 (p < 0.001), SD2 (p < 0.001), ApEn (p < 0.05) and the slope of the power law (p < 0.001) of the analysis of HRV were lower in the patients with TLE than in the control subjects. In patients with hippocampal sclerosis (see chapter 5.5.) the mean values of nearly all the parameters of analysis of HRV were smaller than those of the patients without hippocampal sclerosis. However, the differences did not reach statistical significance (Table 14).
Figure 5. Spectral analysis of HRV in a healthy subject (A) and in a TLE patient (B). The area from 0.005 to 0.04 Hz represents VLF power, the area from 0.04 to 0.15 Hz LF power, and the area from 0.15 to 0.4 Hz HF power (data from Study III).
Figure 6. Poincaré plot from a healthy subject (A) and a TLE patient (B). SD1 indicates SD of instantaneous RR interval variability measured from axis 1, and SD2 indicates SD of long-term continuous RR interval variability measured from axis 2 (data from Study III).
Figure 7. Slopes of power-law relation of a healthy subject (A) and a TLE patient (B) (data from Study III).
Table 14. Analysis of heart rate variation in temporal lobe epilepsy patients with and without hippocampal sclerosis and the control subjects.
| Measure | Patients with HS | Patients with No-HS | All Patients | Control Subjects |
|---|---|---|---|---|
| (n = 8) | (n = 31) | (n = 39) | (n = 34) | |
| RRI | 879 ± 153 | 834 ± 101 | 843 ± 113 | 850 ± 71 |
| SD | 92 ± 19* | 92 ± 30** | 92 ± 28 ** | 113 ± 30 |
| SDNN | 166 ± 69 | 154 ± 38 | 156 ± 45* | 177 ± 44 |
| VLF | 1410 ± 694** | 1714 ± 983** | 1652 ± 935** | 3256 ± 1765 |
| LF | 871 ± 407* | 972 ± 488** | 951 ± 469 ** | 1901 ± 1308 |
| HF | 600 ± 255 | 632 ± 488* | 625 ± 448 * | 710 ± 2050 |
| SD1 | 30 ± 7 | 28 ± 10** | 29 ± 10 ** | 42 ± 22 |
| SD2 | 126 ± 27 | 128 ± 39** | 128 ± 37 ** | 153 ± 38 |
| α2 | 0.98 ± 0.10 | 1.03 ± 0.07 | 1.02 ± 0.10 | 1.0 ± 0.1 |
| ApEn | 1.08 ± 0.18 | 0.97 ± 0.31* | 0.99 ± 0.29 * | 1.15 ± 0.21 |
| Slope of the HRV | -1.37 ± 0.29 | -1.35 ± 0.15** | -1.35 ± 0.19** | -1.20 ± 0.2 |
| For abbreviation see page 66. Values are mean (± SD). HS, hippocampal sclerosis; *, p < 0.05; **, p < 0.001. | ||||