24-hour ECG frequency-domain measures in preeclamptic and healthy pregnantwomen during and after pregnancy

Objective: The aim of the present study was to evaluate the autonomic balan ce in women with preeclampsia and in healthy women during and after pregnan cy by means of a 24-h ECG Holter recording combined with power spectral ana lysis. Methods: Fifteen preeclamptic and 15 healthy women underwent 24-h Holter mo nitoring in the 32nd-36th week of gestation and 3-6 months postpartum. The power spectrum of the maternal electrocardiogram was analyzed with an autor egressive algorithm. Main Outcome Measures: The power spectrum contains two major components: a low-frequency peak, primarily attributed to sympathetic tone, and a high-fr equency peak, reflecting vagal tone. Results: The power spectrum of maternal heart rate variability did not diff er between preeclamptic and normal women during pregnancy. After delivery, the amplitude of all components became significantly higher than those duri ng pregnancy, with one exception: the high-frequency component in the patie nts who had been preeclamptic. In a comparison of the two groups, the high- frequency component after delivery was significantly lower in women who had preeclampsia than in normal healthy women (p = 0.03). Conclusions: During pregnancy, the power spectrum is reduced and cannot be used to distinguish between patients with preeclampsia and normal healthy w omen. Three to 6 months after delivery, the high-frequency component is sti ll reduced in the preeclamptic group of women. This indicates an impaired v agal modulation even in the nonpregnant state in this group of women, unlik e those who had a normotensive pregnancy.