Abstract
Background. Pre-eclampsia is regarded as a primary placental disorder, in which defect placentation causes endothelial and cardiovascular disturbances. Evidence of disturbed neural cardiovascular control in this condition has been suggested, as well as in other hypertensive diseases. The purpose of the present study was to non-invasively evaluate the sympatho-vagal balance during normal and pre-eclamptic pregnancy.
Methods. In twelve healthy pregnant women, thirteen pre-eclaniptic women and ten non-pregnant controls. Heart rate, blood pressure and breathing movements were registered and recorded on B tape recorder for off-line analysis. Variability in heart rate, blood pressure and breathing movements were computed by an autoregressive spectral analysis algorithm. Heart rate variability was quantitated as the area under the spectral curve, and Student's t-test was performed on logarithmic values.
Results. Heart rate variability contained two major components in power, a low frequency peak predominantly attributed to sympathetic tone, and a high frequency peak reflecting vagal tone. Women with pre-eclampsia were characterized by a significantly reduced high frequency peak compared to healthy pregnant (p = 0.03) and non-pregnant (p = 0.02) women. In the low frequency band there were no significant differences in power between the groups. Blood pressure variability did not differ between the groups.
Conclusion. The present results indicate that pre-eclampsia is associated with decreased vagal control of the heart. Furthermore, the results indicate that pregnancy per se does not change sympatho-vagal balance.