Key result
Reactive hyperemia index measured by EndoPAT was significantly reduced at gestational week 28 compared to week 16 (1.63 vs 1.97, p<0.001), contrasting with expected improvements in endothelial function.
Why the study?
Does peripheral arterial tone technology (EndoPAT) accurately assess endothelial function changes throughout pregnancy and post-natally?
Observational (n=172)
Does peripheral arterial tone technology (EndoPAT) accurately assess endothelial function changes throughout pregnancy and post-natally?
Absolute Event Rate: 1.63% vs 1.97%
p-value: p=<0.001
EndoPAT-derived reactive hyperemia index paradoxically deteriorates in mid-pregnancy despite known improvements in endothelial function, suggesting limited specificity of this method in later pregnancy.
EndoPAT feasible for endothelial assessment in pregnancy; leaves open its predictive utility for pre-eclampsia pending validation.
Background: Endothelial dysfunction plays a key role in the pathophysiology of pre-eclampsia. Here we assess a novel non-invasive method for detecting endothelial dysfunction in women throughout pregnancy and post-natally. Design and Method: We studied 142 women at gestational weeks 16 and 28, and 45 women 6 months post-natally. A further 30 non-pregnant women were studied as controls. Endothelial function was assessed with the EndoPAT-2000 device. Pneumatic probes were fitted to the fingers to record the peripheral arterial tone (PAT) signal. Reactive hyperemia index (RHI) was calculated from the ratio of readings before and after 5 minutes of forearm occlusion. Augmentation index (AIx) was calculated from pulse waveforms derived from EndoPAT and from radial applanation tonometry (SphygmoCor). Results: AIx(EndoPAT) correlated with AIx(SphygmoCor) at week 16 (r = 0.33), week 28 (r = 0.65) and post-natally (r = 0.67; all p < 0.001). RHI at all time-points was not related to maternal age, BMI, parity, or history of previous pre-eclampsia. RHI was not different between non pregnant controls and women at gestational week 16, but was significantly reduced at week 28 compared to week 16 (1.63 ± 0.4 vs 1.97 ± 0.7, p < 0.001). There was a corresponding rise in pulse wave amplitude between week 16 and 28 (586 ± 381 vs 1079 ± 421 AU, p < 0.001) indicating vasodilatation in mid-pregnancy. Post-partum, RHI was elevated compared to week 28 (1.95 ± 0.5 vs 1.65 ± 0.4, p < 0.001) with a corresponding reduction in pulse amplitude (552 ± 331 vs 958 ± 357 AU, p < 0.001). AIx(EndoPAT) was reduced in pregnant women at week 16 compared to non-pregnant controls (-13.6 ± 12 vs -1.7 ± 15%) with a further reduction at week 28 (-15.4 ± 12 vs -13.6 ± 12%) and a rise post-natally (1.38 ± 16 vs -15.4 ± 12%; all p < 0.001). Discussion: Previous studies have shown an improvement in endothelial function throughout pregnancy, to allow for the marked increase in blood volume required. We have seen reduced AIx in mid-pregnancy but in contrast a deterioration in RHI that improves post-natally. EndoPAT and other flow-mediated dilatation methods may therefore have a limited specificity for endothelial function assessment in later pregnancy.
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Carty et al. (2010) conducted an observational in Pregnancy (n=172). Pregnancy vs. Non-pregnant state and earlier gestational weeks was evaluated on Reactive hyperemia index (RHI) (p=<0.001). Reactive hyperemia index measured by EndoPAT was significantly reduced at gestational week 28 compared to week 16 (1.63 vs 1.97, p<0.001), contrasting with expected improvements in endothelial function.
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