Objectives: To determine if the normal gestational changes in mechanical properties of the arterial system are altered in pre-eclampsia.
Design: Prospective controlled observational study.
Setting: University urban tertiary medical centre.
Population: Eleven pre-eclamptics and 10 chronic hypertensives with superimposed pre-eclampsia were compared with 14 normotensive gravidas experiencing preterm labour, all receiving MgSO(4). Two additional control groups were studied as well: (A) nine normal pregnant women receiving neither magnesium nor epidural, for baseline comparisons; and (B) eight normotensive gravidas receiving epidural anaesthesia.
Methods: Two-dimensional targeted M-mode echocardiograms and continuous wave Doppler velocity were used to obtain instantaneous pressure and flow data. Total vascular resistance (TVR) quantified the steady component of systemic arterial load; pulsatile arterial load was characterised by global arterial compliance (AC), aortic input impedance spectrum (Z(1)) and characteristic impedance (Z(0)).
Main outcome measures: TVR, AC, Z(1), Z(0).
Results: Controls, pre-eclamptics and chronic hypertensives with superimposed pre-eclampsia, respectively: TVR index 1328 [299], 1973 [609]*, 2428 [562]*(,#) dyn second cm(-5) m(2); AC area index 1.69 [0.46], 1.19 [0.46]*, 0.93 [0.38]* mL mmHg(-1) m(-2); Z(0) index 253.2 [61.3], 327.0 [135.1], 307.5 [130.9] dyn second cm(-5) m(2); and Z(1) index 184.2 [56.5], 283.6 [81.6]*, 357.1 [119.5]* dyn second cm(-5) m(2) (*P < 0.05 vs control;(#)P < 0.05 vs pre-eclampsia). Normal gravidas (in secondary controls group A) had decreased mean systolic and diastolic blood pressures, and increased AC and cardiac indices, compared with women receiving magnesium tocolysis, verifying the need for these primary controls. No differences were noted between normotensive gravidas receiving epidural anaesthesia (secondary controls group B) and the non-anesthetised controls (group A), eliminating epidural as a confounder.
Conclusions: The normal gestational changes in systemic arterial mechanical properties are significantly altered in pre-eclampsia and these alterations are more marked with superimposed hypertensive disease.