Peripheral arterial tone: assessment of microcirculatory function in pregnancy

Endothelial dysfunction is known to play a key role in the pathogenesis of preeclampsia, but the majority of methods for its detection are too invasive to be used in pregnancy. In this study we report a novel method - peripheral arterial tonometry (PAT) - for examining microcirculatory function in pregnancy.

One hundred and eighty women with at least two risk factors for preeclampsia were examined at gestational weeks 16 and 28; 80 women were examined at 6-9 months postnatally. Twenty-four women developed preeclampsia or pregnancy-induced hypertension (cases), 156 remained normotensive (controls). PAT was measured using fingertip pneumatic probes; after baseline recordings the study arm was occluded with a blood pressure cuff then released after 5 min, causing reactive hyperaemia. PAT recordings pre and post occlusion were used to generate the reactive hyperaemia index (RHI).

RHI was significantly lower at gestational week 28 compared to week 16, both in cases and controls. Baseline pulse amplitude was significantly higher at week 28 compared to week 16. There was no difference in RHI at either week 16 or 28 between cases and controls. Postnatally, there was no difference in RHI between cases and controls, but baseline pulse amplitude was lower in affected women.

PAT and other methods which rely on flow-mediated dilatation for detection of endothelial dysfunction are less likely to be reliable in later pregnancy, when women are more vasodilated. PAT did not predict the development of hypertensive pregnancy complications, but demonstrated a relative peripheral vasoconstriction in affected women postnatally.