PREGNANCY INDUCED HYPERTENSION(PIH)AND ALTERED FRACTAL CORRELATION BEHAVIOR IN FETAL HEART RATE(FHR)VARIABILITY

초록

Objectives: The aim of this study was to test whether the statistical, spectral irregular, and fractal correlation behaviors in FHR variaability may be changed in the fetuses of PIH mothers. Study Methods: Sixty fetuses who aged over 30 weeks and were not associated intrauterine growth restriction and whose mothers had mild PIH were studied. Three hundred gestational age-matched normal control fetuses were also included. We selected 5000 points of their FHR and calculated the power spectrum, approximate entropy short-(α1 ≤80bpm)and long-(α2 > 80bpm)term fractal scaling exponent. The approximate entropy, α1 and α2 reflect irregularity, short-term correlation and long-term correlation, respectively. Results: There were no significant differences in the mean (143bpm±0.4 vs 141.9bpm±1.1), variance(43.2bpm2 ±2.2 vs 47.8bpm2 ±5.9), low-(131.0msec2 ±5.6 vs 138.5msec2 ± 12.2) and high-(23.7msec2 ±1.0 vs 27.7msec2 ±2.1) frequency power, and approximate entropy (0.716 ±0.011 vs 0.732 ±0.025) of the FHR between the mild PIH and the control group. However α1 of the PIH group was significantly lower than α1 of the control group (1.368 ±0.015 vs 1.481 ±0.006, p<0.0001) but α2 of the PIH group was significantly higher than α2 of the control group (0.926 ±0.022 vs 0.780 ±0.012, p<0.0001). Conclusions: Among the various heart rate variability indices, only short and long-term fractal scaling exponent showed significant differences between the FHR of fetuses of mild PIH mothers and that of normal fetuses. PIH makes FHR less temporally correlated on short-term scale and more temporally correlated on long-term scale.