Configuration of the microcirculation in pre-eclampsia: possible role of the venular system

The microcirculation: master in normal pregnancy, puppet in preeclampsia

BACKGROUND

The microcirculation is studied sparsely in the field of maternal hemodynamics. With nailfold video capillaroscopy, further insight is possible in this interesting field within maternal hemodynamics.

OBJECTIVE

This study aimed to investigate the association between functional parameters of the microcirculation and the systemic cardiovascular system in pregnant women at risk for gestational hypertension disorders.

STUDY DESIGN

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

RESULTS

In normal pregnancies, a positive association was observed between the capillary bed surface and total vascular resistance (1.807; P=.01) and a negative association between capillary density and cardiac output (-0.269; P=.037). In preeclampsia, a negative association was observed between capillary density and mean arterial pressure (-0.5649; P=.010), and between capillary diameter and cardiac output (-0.165; P=.032).

CONCLUSION

The finding of a reduction in capillary density with an increase in blood pressure in preeclampsia is similar to observations in chronic hypertension. This is considered to be the result of capillary closure after the constriction of the precapillary arterioles. However, in normal pregnancy, the increase in capillary bed surface with rising vascular resistance can only be explained by the primary role of microcirculation in preventing capillary overflow via stimulation of arteriolar constriction. These observations elucidate the earliest hemodynamic origins of hypertension at the microcirculatory level in preeclampsia.

Conjunctival microcirculation in ocular and systemic microvascular disease

The conjunctival microcirculation is an accessible complex network of micro vessels whose quantitative assessment can reveal microvascular haemodynamic properties. Currently, algorithms for the measurement of conjunctival haemodynamics use either manual or semi-automated systems, which may provide insight into overall conjunctival health, as well as in ocular and systemic disease. These algorithms include functional slit-lamp biomicroscopy, laser doppler flowmetry, optical coherence tomography angiography, orthogonal polarized spectral imaging, computer-assisted intravitral microscopy, diffuse reflectance spectroscopy and corneal confocal microscopy. Furthermore, several studies have demonstrated a relationship between conjunctival microcirculatory haemodynamics and many diseases such as dry eye disease, Alzheimer's disease, diabetes, hypertension, sepsis, coronary microvascular disease, and sickle cell anaemia. This review aims to describe conjunctival microcirculation, its characteristics, and techniques for its measurement, as well as the association between conjunctival microcirculation and microvascular abnormalities in disease states.

Placental syndromes and long-term risk of hypertension

Higher blood pressure prior to pregnancy is associated with increased risk of placental abruption, hypertension and preeclampsia, preterm delivery and fetal growth restriction. These conditions are jointly termed placental syndromes as they are characterised by impaired placentation and early placental vascularization. Placental syndromes are associated with an increased maternal risk of progression to hypertension and cardiovascular disease (CVD) in later life. Women affected by both a clinical placental syndrome and with evidence of placental maternal vascular malperfusion (MVM) have a particularly high risk of hypertension and CVD. Yet whether placental impairment and clinical syndromes are causes or consequences of higher blood pressure in women remains unclear. In this review, we address the relationship between blood pressure and maternal health in pregnancy. We conclude that there is a pressing need for studies with a range of detailed measures of cardiac and vascular structure and function taken before, during and after pregnancy to solve the 'chicken and egg' puzzle of women's blood pressure and pregnancy health, and to inform effective precision medicine prevention and treatment of both placental syndromes and chronic hypertension in women.

Adverse pregnancy outcomes and future risk of heart failure

PURPOSE OF REVIEW

Cardiovascular disease (CVD) is the leading cause of death in women. Women with history of adverse pregnancy outcomes (APOs) have approximately two-fold risk of future CVD, but until recently the association with future heart failure (HF) was unclear. Here, we summarize evidence for associations of APOs with HF, potential underlying mechanisms, and future directions for clinical translation.

RECENT FINDINGS

Women with history of hypertensive disorders of pregnancy (HDPs) have roughly two-fold risk of future HF compared with other parous women even after accounting for interval development of coronary artery disease. The HDPs portend heightened risk of HF with both reduced and preserved ejection fraction. Gestational diabetes mellitus (GDM) and other APOs such as preterm delivery, small-for-gestational-age delivery, and placental abruption may also confer additional risk for HF development. Possible underlying mechanisms linking APOs to HF include shared upstream risk factors and genetics, accelerated development of cardiometabolic risk factors postpartum, persistent endothelial and microvascular dysfunction, and impaired natriuretic peptide signaling.

SUMMARY

History of APOs, including HDPs and GDM, confer increased risk for development of HF years after delivery. Further research is needed to define strategies to optimize prepregnancy and postpartum cardiovascular health toward HF prevention.

Nailfold Video Capillaroscopy in Pregnant Women With and Without Cardiovascular Risk Factors

Objective

To evaluate microvasculature in pregnant women with and without cardiovascular risk factors.

Design

Cross-sectional, observational study.

Population

Women were recruited at the outpatient clinic for high risk prenatal care. Out of a total of 345 women assessed at first and/or second and/or third trimester, 169 women without and 176 with cardiovascular risk factors were included.

Methods

Nailfold video capillaroscopy (NVC) measurements were performed at magnification of 200x at all fingers except thumbs. Images were stored for offline measurement of capillary density (CDe) and capillary diameters (CDi). Maternal anthropometrics, obstetric, and medical history were used for categorization in low and high cardiovascular risk. Comparison between groups and trimesters, with respect to pregnancy outcome, was performed using linear mixed model analysis.

Results

Women with a high risk cardiovascular profile show higher CDe, regardless of pregnancy outcome. CDi drops during pregnancy, with lowest CDi in third trimester in patients with preeclampsia. Capillary bed (CB), as a composite of CDe and CDi, is stable during pregnancy in women with low risk cardiovascular profile. In women with high risk cardiovascular profile, CB drops from the first to the second trimester, regardless of pregnancy outcome. Only in women with pre-eclampsia, the CB is lower in the third trimester as compared to the first trimester.

There is an inverse association between CDe and mean arterial pressure (MAP) in women with high cardiovascular risk and pre-eclampsia.

Conclusion

Microcirculation is altered during the course of pregnancy and microcirculatory behavior is different in patients with low and high cardiovascular risk profile, as well as in patients with preeclampsia.

Maternal Vascular Lesions in the Placenta Predict Vascular Impairments a Decade After Delivery

Women with adverse pregnancy outcomes later experience excess hypertension and cardiovascular disease, but how the events are linked is unknown. Examination of the placenta may provide clues to vascular impairments after delivery. Maternal vascular malperfusion lesions (MVMs) were abstracted from clinical reports, validated and characterized using clinical guidelines and severity score. A total of 492 women (170 with MVMs and 322 without MVMs) participated in a study visit 8 to 10 years after delivery to assess blood pressure, cardiometabolic factors, and sublingual microvascular features using sidestream dark field imaging. Covariates included age, race, adverse pregnancy outcomes (preeclampsia, small for gestational age, and preterm birth), and health behaviors. Women with versus without MVM had a distinct sublingual microvascular profile comprised of (1) lower microvascular density (-410 μm/mm², P=0.015), (2) higher red blood cell filling as a marker of perfusion (2%, P=0.004), and (3) smaller perfused boundary region (-0.07 µm, P=0.025) as a measure of glycocalyx integrity, adjusted for covariates including adverse pregnancy outcomes. Women with MVM also had higher adjusted diastolic blood pressure (+2.6 mm Hg, P=0.021), total and LDL (low-density lipoprotein)-cholesterol (+11.2 mg/dL, P=0.016; +8.7 mg/dL, P=0.031). MVM associations with subsequent cardiovascular measures did not vary by type of adverse pregnancy outcome, except among women with preterm births where blood pressure was higher only among those with MVM. Results were similar when evaluated as MVM severity. A decade after delivery, women with placental vascular lesions had an adverse cardiovascular profile comprised of microvascular rarefaction, higher blood pressure and more atherogenic lipids. Placental histopathology may reveal a woman's early trajectory toward subsequent vascular disease.

Capillaroscopy in pregnancy

INTRODUCTION

In pregnancy, the circulatory system undergoes profound adaptation to meet the requirements in blood supply for the mother and the foetus. With the development of new techniques, research of the microcirculatory changes becomes available. This expert review gives an overview of the current evidence in the field of capillaroscopy. The aim of this review is to summarize the available techniques in the assessment of the microcirculation during pregnancy. Areas covered: A literature search was done, using the strategy: (microcirculation OR capillary OR capillaries OR capillaroscopy) AND pregnancy AND (density OR diameter OR count OR number). All articles were screened and all English articles were considered, when containing information regarding imaging of capillaries. Only structural parameters were considered, functional parameters (e.g. flow velocity) were not considered. Reference search was undertaken after reading full text articles. Articles from reference search underwent same selection criteria as in the primary search. Expert commentary: With growing insight in microcirculatory changes in hypertensive pregnancy conditions, the field of capillaroscopy will become more important in future. The technique is feasible and easy to use in clinical practice as well as in research setting. The first step, necessary to perform further research in this field in future, is to get consensus in technique to perform capillaroscopy and in methods to quantitatively and qualitatively describe the observed changes in microvasculature.

Surgical management of massive labial edema in a gravid preeclamptic diabetic

Background. Massive labial edema is a rare complication during pregnancy that can jeopardize vaginal delivery, as well as leading to maternal and fetal morbidity. It can be related to systemic pathologies, but has been commonly associated with preeclampsia and diabetes. This increased and sometimes longstanding pressure may result in a “labial compartment syndrome” leading to microvascular damage and tissue necrosis if not resolved in a timely fashion. Case. Massive labial edema was treated first conservatively and then surgically in a gravid diabetic patient with severe preeclampsia. Immediately after Cesarean section, the labial compartment syndrome was relieved surgically and resolved rapidly. Conclusion. When conservative attempts at management of labial edema fail, or rapid resolution is critical to maternal and fetal outcome, surgical alternatives should be considered.

Is there a correlation between maternal venous hemodynamic dysfunction and proteinuria of preeclampsia?

OBJECTIVES

To evaluate in early and late preeclampsia a correlation of maternal venous Doppler flow characteristics with biochemical parameters in maternal serum and urine, or with gestational outcome.

STUDY DESIGN

In this observational cross-sectional study, renal interlobar vein impedance index (RIVI) was measured according to a standardised protocol for combined electrocardiogram-Doppler ultrasonography in 86 women with uncomplicated pregnancy, 78 women with late onset preeclampsia (≥34w) and 67 with early onset preeclampsia (<34w). For each group, maternal age, pre-gestational BMI and parity were recorded together with birth weight and -percentile. For both early onset and late onset preeclampsia, maternal serum was analysed for thrombocyte count and concentrations of creatinine, ASAT, ALAT and uric acid and 24h urine collections were analysed for creatinine clearance and proteinuria (mg/24h). A non-parametric Mann-Whitney U-tests was performed for continuous data and a Fisher's exact tests for categorical data. Significant linear dependence between variables was identified using Pearson's correlation coefficient at nominal level a=0.05.

RESULTS

Proteinuria was higher in early onset than in late onset preeclampsia (1756mg [838-6116mg] versus 877mg [416-1696mg], p<0.001), and this was also true for RIVI in both left (0.45 [0.40-0.55] versus 0.41 [0.35-0.45], p=0.001) and right kidney (0.45 [0.39-0.55] versus 0.38 [0.30-0.43], p<0.001). In our data set, there was a significant correlation between proteinuria and RIVI of left (correlation coefficient=0.172, p=0.036) and right kidney (correlation coefficient=0.218, p=0.009) in late onset but not early onset preeclampsia.

CONCLUSION

Maternal RIVI may correlate with proteinuria of late onset preeclampsia.

Microcirculation in women with severe pre-eclampsia and HELLP syndrome: a case-control study

OBJECTIVE

To compare microcirculatory perfusion in women with severe pre-eclampsia against that in healthy pregnant women, and secondly in women with severe pre-eclampsia with or without HELLP syndrome (haemolysis, elevated liver enzymes, and low platelets).

DESIGN

Case-control study.

SETTING

University Hospital Rotterdam, the Netherlands.

POPULATION

Twenty-three women with severe pre-eclampsia and 23 healthy pregnant controls, matched for maternal and gestational age. Out of the 23 women with severe pre-eclampsia, ten presented with HELLP syndrome.

METHODS

Microcirculation was analysed sublingually by a non-invasive sidestream dark-field imaging device (SDF).

MAIN OUTCOME MEASURES

Perfused vessel density (PVD), microcirculatory flow index (MFI), and heterogeneity index (HI) were calculated for both small vessels (∅ < 20 μm; capillaries) and non-small vessels (∅ > 20 μm; venules and arterioles).

RESULTS

There were no significant differences between women with severe pre-eclampsia and healthy controls. Women with pre-eclampsia and HELLP syndrome showed a reduced PVD (P = 0.045), MFI (P = 0.008), and increased HI (P = 0.002) for small vessels, as compared with women with pre-eclampsia but without HELLP syndrome.

CONCLUSIONS

Sidestream dark-field is a novel, promising technique in obstetrics that permits the non-invasive evaluation of microcirculation. We did not observe major differences in sublingual microcirculatory perfusion between women with severe pre-eclampsia and healthy pregnant controls. In women with severe pre-eclampsia, the presence of HELLP syndrome is characterised by impaired capillary perfusion.

Prevention of vascular dysfunction after preeclampsia: a potential long-term outcome measure and an emerging goal for treatment

Preeclampsia is increasingly being recognised as more than an isolated disease of pregnancy. In particular, preeclampsia has emerged as an independent risk factor for maternal cardiovascular disease and has recently been recognised as a risk factor for cardiovascular disease in children exposed in utero. Preeclampsia and cardiovascular disease may share important pathophysiological and molecular mechanisms and further investigation into these is likely to offer insight into the origins of both conditions. This paper considers the links between cardiovascular disease and preeclampsia and the implication of these findings for refinement of the management of patients whose care is complicated by preeclampsia.

Role of dysfunctional maternal venous hemodynamics in the pathophysiology of pre-eclampsia: a review

The venous compartment has an important function in regulation and control of cardiac output. Abnormalities of cardiac output have been found in early gestational stages of both early- and late-onset pre-eclampsia. The venous compartment also maintains the balance between circulating and non-circulating blood volumes and regulates the amount of reserve blood stored in the splanchnic venous bed. It is well known that adaptive regulation of maternal blood volume is disturbed in pre-eclampsia. Abnormal venous hemodynamics and venous congestion are responsible for secondary dysfunction of several organs, such as the kidneys in cardiorenal syndrome and the liver in cardiac cirrhosis. Renal and liver dysfunctions are among the most relevant clinical features of pre-eclampsia. Doppler sonography studies have shown that the maternal venous compartment is subject to gestational adaptation, and that blood flow characteristics at the level of renal interlobar and hepatic veins are different in pre-eclampsia compared with uncomplicated pregnancy. In comparison to late-onset pre-eclampsia, in early-onset pre-eclampsia venous Doppler flow abnormalities are more prominent and present up to weeks before clinical symptoms. This paper reviews the growing evidence that dysfunction of maternal venous hemodynamics is part of the pathophysiology of pre-eclampsia and may perhaps be more important than is currently considered. Doppler sonography is a safe and easily performed method with which to study maternal venous hemodynamics. Therefore, exploring the role of maternal venous hemodynamics using Doppler sonography is an exciting new research topic for those who are interested in cardiovascular background mechanisms, as well as prediction and clinical work-up of pre-eclampsia.

Maternal renal interlobar vein impedance index is higher in early- than in late-onset pre-eclampsia

OBJECTIVES

To test the hypothesis that Doppler characteristics of maternal renal interlobar veins (RIV) are different between pregnancies affected by early-onset pre-eclampsia (EP) and those affected by late-onset pre-eclampsia (LP).

METHODS

A gestational age of 34 weeks was considered to differentiate EP from LP. All women had a renal duplex scan according to a standard protocol, with known intraobserver correlation coefficient (0.88). Maximum (Vmax) and minimum (Vmin) RIV velocities were measured on two occasions (between 28 and 32 and between 34 and 37 weeks) in 18 women with uncomplicated pregnancy (UP). In women with EP (n = 32) or LP (n = 41), these variables were measured once, within 3 days following hospital admission. Delta velocity (DeltaV) was calculated as Vmax - Vmin and the RIV impedance index (RIVI) was calculated as DeltaV/Vmax. Data on neonatal outcome and maternal renal function were obtained for UP and those with EP and LP, and group-specific means +/- SD were calculated and compared.

RESULTS

Compared with UP, the RIVI of both left and right kidneys was higher in those with EP (0.49 +/- 0.13 vs. 0.36 +/- 0.04, P = 0.0001, and 0.46 +/- 0.15 vs. 0.33 +/- 0.04, P = 0.0008) and in those with LP (0.41 +/- 0.07 vs. 0.37 +/- 0.06, P = 0.04, and 0.38 +/- 0.12 vs. 0.30 +/- 0.05, P = 0.009). RIVI was higher in pregnancies with EP than in those with LP (P < or = 0.01), and this difference was associated with lower median birth-weight percentiles (22.5 (interquartile range (IQR), 15-35) vs. 40.0 (IQR, 12-55), P = 0.01), higher maternal serum uric acid concentrations (419 +/- 84 vs. 374 +/- 85 micromol/L, P = 0.03) and higher proteinuria (4131 +/- 3885 vs. 1190 +/- 1133 mg/24 h, P < 0.0001).

CONCLUSION

Maternal vascular maladaption in pre-eclampsia is associated with abnormal Doppler findings in the venous compartment. RIVI is higher in EP than in LP pregnancies and this is associated with lower birth-weight percentiles and higher proteinuria.

Abnormal endothelium-dependent microvascular dilator reactivity in pregnancies complicated by normotensive intrauterine growth restriction

OBJECTIVE

Normotensive intrauterine growth restriction and preeclampsia share a similar placenta pathophysiology, whereas maternal clinical manifestations differ. Clinical symptoms of preeclampsia are partly attributed to vascular endothelial dysfunction, but it is unclear whether this phenomenon plays a role in intrauterine growth restriction. Therefore, we investigated microvascular endothelial function in women with intrauterine growth restriction.

STUDY DESIGN

Laser Doppler fluxmetry was used combined with iontophoresis of acetylcholine and sodium nitroprusside, namely, endothelium-dependent and endothelium-independent vasodilators. We studied 12 women with intrauterine growth restriction and 16 controls in the third trimester of pregnancy. All women had prepregnancy body mass indexes < 26.

RESULTS

Acetylcholine-mediated vasodilatation was significantly increased in women with intrauterine growth restriction compared with controls (743% +/- 120% vs 390% +/- 67%, P = .01); sodium nitroprusside-mediated vasodilatation was not different (360% +/- 55% vs 363% +/- 65%, P > .99).

CONCLUSION

Nonobese women with normotensive intrauterine growth restriction show abnormal endothelium-dependent microvascular vasodilatation, suggesting endothelial dysfunction as in preeclampsia. Obviously, for the clinical manifestation of preeclampsia additional factors are required, and a role of metabolic syndrome and obesity has been suggested.