The microcirculation : master in normal pregnancy, puppet in preeclampsia.

Abstract

Objective: To investigate the association between functional parameters of the microcirculation and the systemic cardiovascular system in a population of pregnant women at risk for gestational hypertension disorders.

Study design: For this observational study, women at high cardiovascular risk according to maternal anthropometrics, obstetric and medical history, were recruited at random gestational age depending on time of referral to the outpatient clinic for high risk prenatal care at Ziekenhuis Oost Limburg, Genk Belgium. After birth, data of maternal and neonatal outcome were obtained from the hospital records: only women with normal pregnancy (n = 142) and with preeclampsia (n = 34) were included in this analysis. Nailfold video capillaroscopy measurements were performed in first and/or second and/or third trimester. Video magnification of 200x was used at all fingers except thumbs, and stored images were analyzed offline. Capillary density was counted (n/mm²), mean capillary diameter measured (μm) and capillary bed was calculated as density x diameter. Cardiac output and total peripheral resistance were measured using impedance cardiography, together with sphygmomanometric blood pressure measurement. Linear mixed model for repeated measures was employed to investigate the association between the microvascular and macrovascular parameters. No correction for multiple testing was used.

Results: In normal pregnancies, a positive association was observed between capillary bed and total vascular resistance (1.807, p =0.01), and a negative association between capillary density and cardiac output (-0.269, p =0.037). In preeclampsia, a negative association was observed between capillary density and mean arterial pressure (-0.5649, p = 0.010), and between capillary diameter and cardiac output (-0.165, p=0.032).

Conclusion: A reduction of capillary density with increase of blood pressure in preeclampsia is similar to observations in chronic hypertension. Here, this is considered the result of capillary closure after constriction of precapillary arterioles. In normal pregnancy however, the increase of the capillary bed with rising vascular resistance can only be explained by a primary role for the microcirculation, preventing capillary overflow via stimulation of arteriolar constriction. These observations enlighten the very first hemodynamic origins of hypertension at the level of the microcirculation in preeclampsia.