Heart rate and blood pressure variabilities are increased in pregnancy-induced hypertension

Our purpose was to study whether cardiovascular changes in pregnancy-induced hypertension are associated with the increase in sympathetic control of hemodynamics and change in sympathovagal balance.

Fourteen women with pregnancy-induced hypertension and 16 women with uncomplicated pregnancies of similar duration were studied. Electrocardiographic signals and arterial blood pressure (Finapres monitor, Ohmeda) were continuously measured noninvasively throughout the study. Heart rate and blood pressure were measured while the subject was breathing (1) with her normal tidal volume at a frequency of 15 breaths per minute and (2) as deeply as possible at a frequency of six breaths per minute. Heart rate and systolic blood pressure variability were calculated with use of the autoregressive model of spectral analysis.

Heart rate and systolic blood pressure variabilities were significantly increased in women with pregnancy-induced hypertension compared with normotensive pregnant women. This increase was greatest in the high frequency component of heart rate variability (p = 0.02) while the women were breathing with a normal tidal volume. Further, the medium frequency (p = 0.03) and high-frequency variabilities (p = 0.03) of systolic blood pressure were significantly increased in women with preeclampsia compared with normotensive pregnant subjects.

Neural control of the heart rate and blood pressure are disturbed in pregnancy-induced hypertension, as shown by increased heart rate and blood pressure variability. Both the sympathetic and parasympathetic control of the heart rate and blood pressure appear to be increased. The maladaptation of the cardiovascular system in women with pregnancy-induced hypertension is manifested as a lack of the physiologic decline in cardiovascular oscillations.