DYNAMIC AND STEADY-STATE RESPONSE OF HEART-RATE TO ORTHOSTATIC STRESSIN NORMOTENSIVE AND HYPERTENSIVE PREGNANT-WOMEN

We determined the dynamic and steady state responses of heart rate (HR ) to orthostatic stress (standing up) in normotensive and hypertensive pregnant women, Using a continuous recording with servo-photosphygmog raphy, HR response to change in posture from left lateral recumbent po sition to standing was analysed. The subjects were divided into five g roups comprising: Groups I, II and III: normotensive pregnant women in each of the three trimesters of pregnancy (total n = 77); Group IV: w omen with gestational proteinuric hypertension (GPH) in the third trim ester (n = 16); Group V: age-matched non-pregnant normotensive control s (n = 15), The HR reacted with a typical overshoot response to this o rthostatic change with HR rising to a peak and then settling to a new but higher steady state, Change in steady state HR from lying to stand ing (delta HR), rate of rise of HR in response to standing (i.e. the a cceleration slope (HR(on))), and rate of fall of HR after reaching the peak (i.e. deceleration slope (HR(off))) were evaluated from standing heart rate time curves, HR(on) in response to standing showed a downw ard trend with gestation (ANOVA, P < 0.05) in normotensive gravida. Th e deceleration slope (HR(off)) showed a distinct gestational age-relat ed decrease from first to third trimester in normotensive women (ANOVA , P < 0.01). The most striking observation was that the slope of HR(of f) for the GPH group was significantly steeper than that of normotensi ve women of comparable gestational age (unpaired t-test P < 0.01) and approximated to that of the non-pregnant group. The difference in HR r esponse between normotensive women and those with GPH in the third tri mester suggests it may have potential as a new marker for pre-eclampsi a.