Low Plasma Volume Coincides With Sympathetic Hyperactivity and Reduced Baroreflex Sensitivity In Formerly Preeclamptic Patients

Cardiovascular and renal health: Preeclampsia as a risk marker

BACKGROUND

Cardiovascular (CVD) and chronic kidney disease (CKD) in women have unique risk factors related to hormonal status and obstetric history that must be taken into account. Pregnancy complications, such as preeclampsia (PE), can reveal a subclinical predisposition for the development of future disease that may help identify women who could benefit from early CVD and CKD prevention strategies.

MATERIALS AND METHODS

Review of PE and its association with future development of CVD and CKD.

RESULTS

Multiple studies have established an association between PE and the development of ischemic heart disease, chronic hypertension, peripheral vascular disease, stroke and CKD. It has not been sufficiently clarified if this relation is a causal one or if it is mediated by common risk factors. Nevertheless, the presence of endothelial dysfunction and thrombotic microangiopathy during pregnancies complicated with PE makes us believe that PE may leave a long-term imprint. Early identification of women who have had a pregnancy complicated by PE becomes a window of opportunity to improve women's health through adequate follow-up and targeted preventive actions. Oxidative stress biomarkers and vascular ultrasound may play a key role in the early detection of this arterial damage.

CONCLUSIONS

The implementation of preventive multidisciplinary targeted strategies can help slow down CVD and CKD's natural history in women at risk through lifestyle modifications and adequate blood pressure control. Therefore, we propose a series of recommendations to guide the prediction and prevention of CVD and CKD throughout life of women with a history of PE.

Low Plasma Volume and Increased Pressure Load Relate to Concentric Left Ventricular Remodeling After Preeclampsia: A Longitudinal Study

Background During uncomplicated pregnancy, left ventricular remodeling occurs in an eccentric way. In contrast, during preeclamptic gestation, the left ventricle hypertrophies concentrically, concurrent with loss in circulatory volume and increased blood pressure. Concentric cardiac structure persists in a substantial proportion of women and may be associated with pressure and volume load after preeclampsia. We hypothesize that low volume load, as indicated by plasma volume (PV) after preeclampsia and increased pressure load, is associated with remote concentric remodeling. Methods and Results In this longitudinal cohort study, we included 100 formerly preeclamptic women. Two visits were performed: at 0.8 years postpartum and at 4.8 years postpartum. During visit 1, we measured blood pressure and PV (I125 dilution technique, low PV ≤48 mL/kg lean body mass). During the second visit, we assessed cardiac geometry by cardiac ultrasound. Concentric remodeling was defined as relative wall thickness >0.42 and left ventricular mass index ≤95 g/m2. We adjusted multivariable analysis for primiparity, systolic blood pressure, PV mL/kg lean body mass, and antihypertensive medication at visit 1. Low PV is associated with remote concentric remodeling (odds ratio [OR], 4.37; 95% CI, 1.06-17.40; and adjusted OR, 4.67; 95% CI, 1.02-21.42). Arterial pressure load (systolic, diastolic, and mean arterial pressure) is also associated with development of concentric remodeling (OR, 1.15 [95% CI, 0.99-1.35]; OR, 1.24 [95% CI, 0.98-1.58]; and OR, 1.20 [95% CI, 0.98-1.47], respectively). Conclusions In former preeclamptic women, development toward left ventricular concentric remodeling is associated with low volume load and increased pressure load.

Preeclampsia beyond pregnancy: long-term consequences for mother and child

Preeclampsia is defined as new-onset hypertension after the 20th wk of gestation along with evidence of maternal organ failure. Rates of preeclampsia have steadily increased over the past 30 yr, affecting ∼4% of pregnancies in the United States and causing a high economic burden (22, 69). The pathogenesis is multifactorial, with acknowledged contributions by placental, vascular, renal, and immunological dysfunction. Treatment is limited, commonly using symptomatic management and/or early delivery of the fetus (6). Along with significant peripartum morbidity and mortality, current research continues to demonstrate that the consequences of preeclampsia extend far beyond preterm delivery. It has lasting effects for both mother and child, resulting in increased susceptibility to hypertension and chronic kidney disease (45, 54, 115, 116), yielding lifelong risk to both individuals. This review discusses recent guideline updates and recommendations along with current research on these long-term consequences of preeclampsia.

The role of hepatic sinusoidal obstruction in the pathogenesis of the hepatic involvement in HELLP syndrome: Exploring the literature

AIM

This study aims to determine, based on existing data, whether the mechanism resulting in liver dysfunction in HELLP syndrome resembles that in Sinusoidal Obstruction Syndrome (SOS).

BACKGROUND

HELLP syndrome is a serious pregnancy disorder with high maternal and perinatal morbidity and mortality rates. Because of poor insight in its pathophysiology, particularly that of the liver involvement, clinical management is limited to symptomatic treatment, often followed by termination of pregnancy. SOS is a rare, potentially life-threatening complication of radio and/ or chemotherapy in the preparation of hematopoietic cell transplantation. The etiology of liver dysfunction in SOS is - unlike that in HELLP syndrome - better-understood and seems to be initiated by direct toxic damage and demise of endothelial cells, causing hepatic sinusoidal obstruction and ischemia.

METHODS

We searched Pubmed, Embase and Cochrane for reports on the etiology of HELLP and SOS. This yielded 73 articles, with 14 additional reports from the references listed in these articles.

RESULTS

The dysfunctional placenta in women developing HELLP initiates a cascade of events that eventually results in liver dysfunction. The placenta releases, besides anti-angiogenetic factors, also necrotic debris and cell-free DNA, a mixture that not only induces systemic endothelial dysfunction as in preeclampsia, but also a systemic inflammatory response. The latter aggravates the endothelio-toxic effects in the systemic cardiovascular bed, amplifying the already increased pro-thrombotic conditions. Particularly in microcirculations with extremely low shear forces, such as in the hepatic sinusoids, this will facilitate microthrombi formation and fibrin deposition eventually resulting in obstruction of the sinusoids similar as in SOS. The latter causes ischemic damage and progressive demise of hepatocytes.

CONCLUSION

The available information supports the concept that the liver damage in HELLP and SOS results from sinusoidal ischemia, presumably resulting from partially overlapping pathophysiological mechanisms.

Decreased heart rate recovery in women with a history of pre-eclampsia

BACKGROUND

A growing body of literature has reported that a history of pre-eclampsia (PE) increases a woman's long-term risk of cardiovascular diseases (CVD). Autonomic nervous system dysfunction was found to be significant in this specific population, but most studies observed the role of sympathetic over-activation. The aim of this study was to assess whether parasympathetic impairment was involved in women 1 year after PE, and heart rate recovery (HRR) was used to represent parasympathetic tone.

STUDY DESIGN

47 women with previous PE (PE group) and 58 women with a healthy pregnancy (control group) were examined. Blood pressure levels, lipid profiles, homeostasis model assessment of insulin resistance (HOMA-IR), inflammatory biomarkers and HRR were compared between the two groups, and the association between the biochemical parameters and HRR in the PE group was evaluated.

RESULTS

Compared with the Control group, body mass index, 24-h mean diastolic blood pressure, low-density lipoprotein cholesterol and Ln(HOMA-IR) were higher, and HRR was slower in the PE group. Furthermore, body mass index, total cholesterol, and Ln(HOMA-IR) were independent determinants of HRR in the PE group according to multiple regression analysis.

CONCLUSIONS

Our findings suggest that parasympathetic impairment is involved in this specific female population, and its close association with body mass index, total cholesterol and insulin resistance might contribute to an increased risk of CVD development in women with PE history.

Time course of changes in maternal left ventricular function during subsequent pregnancy in women with a history of gestational hypertensive disorders

Women with a history of gestational hypertensive disorders (GHD) are at increased risk for developing perinatal cardiovascular complications (e.g., gestational hypertension, preeclampsia, etc.) in subsequent pregnancies. The underlying mechanisms remain uncertain, but impaired maternal left ventricular function may be one contributing factor for these complications. We evaluated the time course of changes in left ventricular function before, during, and after pregnancy in women with prior GHD. Sixteen women with a history of GHD (the high-risk group) and 25 women without such a history (controls) were enrolled. Resting hemodynamic and echocardiographic measurements were longitudinally performed before pregnancy, during early pregnancy (4-8 wk of gestation), during late pregnancy (32-36 wk of gestation), and postpartum (6-10 wk after delivery). Pregnancy outcomes were obtained after delivery. At prepregnancy, there was no difference in blood pressure and heart rate between the groups. Corrected isovolumic relaxation time was longer, E/ e' was larger, and Tei index was greater in the high-risk group than controls. Moreover, the rate of GHD during the study was significantly greater in the high-risk group than controls [odds ratio = 8.94 (95% confidence interval: 1.55-51.5), P = 0.007]. Multiple logistic regression analysis adjusted for age demonstrated that prepregnancy E/ e' was an independent predictor for GHD ( P = 0.017). Thus, women with a history of GHD have modestly impaired cardiac function prepregnancy compared with controls, which identifies an increased susceptibility to developing cardiovascular complications during a subsequent pregnancy.

Cardiovascular Sequels During and After Preeclampsia

Preeclampsia is a pregnancy-specific disorder complicating 2%-8% of pregnancies worldwide and characterized by de novo development of hypertension and proteinuria. Current understanding of the pathophysiology of preeclampsia is limited. A main feature is disrupted spiral artery remodeling in the placenta, which restricts the blood flow to the placenta, which in turn leads to decreased uteroplacental perfusion. Impaired blood flow through the placenta might result in fetal growth restriction and secretion of several factors by the placenta-mainly pro-inflammatory cytokines and anti-angiogenic factors-which spread into the maternal circulation, leading to endothelial dysfunction, which subsequently results in disrupted maternal hemodynamics. To date, no treatment options are available apart from termination of pregnancy. Despite normalization of the maternal vascular disturbances after birth, it has become apparent that formerly preeclamptic women experience an increased risk to develop cardiovascular and kidney disease later in life. One well-accepted concept is that the development of preeclampsia is an indicator of maternal susceptibility to develop future cardiovascular conditions, although the increased risk might also be the result of organ damage caused during preeclampsia. Given the associations between preeclampsia and long-term complications, preeclampsia is acknowledged as woman-specific risk factor for cardiovascular disease. Current research focuses on finding effective screening and prevention strategies for the reduction of cardiovascular disease in women with a history of preeclampsia.

Pregnancy as a critical window for blood pressure regulation in mother and child: programming and reprogramming

Pregnancy is a critical time for long-term blood pressure regulation in both mother and child. Pregnancies complicated by placental insufficiency, resulting in pre-eclampsia and intrauterine growth restriction, are associated with a threefold increased risk of the mother to develop hypertension later in life. In addition, these complications create an adverse intrauterine environment, which programmes the foetus and the second generation to develop hypertension in adult life. Female offspring born to a pregnancy complicated by placental insufficiency are at risk for pregnancy complications during their own pregnancies as well, resulting in a vicious circle with programmed risk for hypertension passing from generation to generation. Here, we review the epidemiology and mechanisms leading to the altered programming of blood pressure trajectories after pregnancies complicated by placental insufficiency. Although the underlying mechanisms leading to hypertension remain the subject of investigation, several abnormalities in angiotensin sensitivity, sodium handling, sympathetic activity, endothelial function and metabolic pathways are found in the mother after exposure to placental insufficiency. In the child, epigenetic modifications and disrupted organ development play a crucial role in programming of hypertension. We emphasize that pregnancy can be viewed as a window of opportunity to improve long-term cardiovascular health of both mother and child, and outline potential gains expected of improved preconceptional, perinatal and post-natal care to reduce the development of hypertension and the burden of cardiovascular disease later in life. Perinatal therapies aimed at reprogramming hypertension are a promising strategy to break the vicious circle of intergenerational programming of hypertension.

Long-term renal and cardiovascular risk after preeclampsia: towards screening and prevention

Preeclampsia (PE) is a hypertensive pregnancy disorder complicating up to 1-5% of pregnancies, and a major cause of maternal and fetal morbidity and mortality. In recent years, observational studies have consistently shown that PE carries an increased risk for the mother to develop cardiovascular and renal disease later in life. Women with a history of PE experience a 2-fold increased risk of long-term cardiovascular disease (CVD) and an approximate 5-12-fold increased risk of end-stage renal disease (ESRD). Recognition of PE as a risk factor for renal disease and CVD allows identification of a young population of women at high risk of developing of cardiovascular and renal disease. For this reason, current guidelines recommend cardiovascular screening and treatment for formerly preeclamptic women. However, these recommendations are based on low levels of evidence due to a lack of studies on screening and prevention in formerly preeclamptic women. This review lists the incidence of premature CVD and ESRD observed after PE and outlines observed abnormalities that might contribute to the increased CVD risk with a focus on kidney-related disturbances. We discuss gaps in current knowledge to guide optimal screening and prevention strategies. We emphasize the need for research on mechanisms of late disease manifestations, and on effective screening and therapeutic strategies aimed at reducing the late disease burden in formerly preeclamptic women.

Maternal cardiac adaptation to subsequent pregnancy in formerly pre-eclamptic women according to recurrence of pre-eclampsia

OBJECTIVES

Left-ventricular remodeling in women with pre-eclampsia (PE) is concentric rather than eccentric, and tends to persist postpartum, particularly after early-onset PE. This study was designed to determine whether prepregnancy cardiac geometry and function along with cardiac adaptation to the subsequent pregnancy in former early-onset PE patients differs between those who do and those who do not develop recurrent PE later on in their second pregnancy.

METHODS

In 51 women with a history of early-onset PE, we performed serial cardiac ultrasound examinations and recorded automated measurements of blood pressure/heart rate before pregnancy and again at three consecutive times in the first half of their subsequent pregnancy. From the hospital records, we retrieved information on pregnancy outcome. We compared intergroup differences in cardiac indices using independent samples t-test, and intergroup differences in prepregnant cardiac ultrasound indices and subsequent pregnancy-induced cardiac adaptive response using repeated-measures ANOVA.

RESULTS

PE recurred in 14/51 (27%) women. Preconception, the recurrent-PE group differed from the non-recurrent-PE group by having a lower left-ventricular mass (LVM) index (28 vs 32 g/m(2.7) , P < 0.05) and stroke volume (68 vs 77 mL, P < 0.05), and a higher resting heart rate (71 vs 64 bpm, P < 0.05). Despite these prepregnancy differences, the pregnancy-induced pattern of cardiac adaptive response was comparable in the two subgroups. After excluding hypertensive women, prepregnancy values for the LVM index remained significantly lower in the recurrent-PE group.

CONCLUSIONS

Women with recurrent PE differed from the non-recurrent-PE group by having a lower LVM index and stroke volume, and a higher heart rate, but they responded to their subsequent pregnancy with a similar pattern of cardiac adaptation.

Cardiovascular effects of aerobic exercise training in formerly preeclamptic women and healthy parous control subjects

OBJECTIVE

Women who have had preeclampsia demonstrate higher prevalence of metabolic syndrome (MetS), impaired vascular function, and increased sympathetic activity and are at increased risk of cardiovascular disease. The aim of this study was to assess the effects of 12 weeks of exercise training (70-80% maximum volume of oxygen utilization) in women who had had preeclampsia on physical fitness, components of MetS, vasculature, and autonomic functions compared with healthy control subjects.

STUDY DESIGN

Our prospective case-control study included 24 normotensive women who had had preeclampsia and 20 control subjects who were matched for age and postpartum interval (all 6-12 months after delivery). Before and after training, we measured all components of MetS (ie, BP, lipids, glucose/insulin, and albuminuria), carotid intima media thickness (IMT) and brachial and superficial femoral artery endothelial function that used flow-mediated dilation (FMD). Autonomic activity was quantified with power spectral analysis (low-frequency/high-frequency power [LF/HF] ratio).

RESULTS

At baseline, women who had had preeclampsia demonstrated higher values of most components of MetS. Compared with the control subjects, women who had had preeclampsia had increased IMT (580 ± 92 μm vs 477 ± 65 μm, respectively), impaired endothelial function (FMD brachial artery, 5.3% ± 2.2% vs 10.8% ± 3.5%, respectively; FMD superficial femoral artery, 4.9% ± 2.1% vs 8.7% ± 3.2%, respectively) and increased LF/HF power ratio (2.2 ± 1.0 vs 1.3 ± 0.4, respectively; all P < .05). In both groups, exercise training decreased values of most components of MetS and IMT, improved FMD, and concurrently reduced LF/HF. Despite these improvements, vascular and autonomic variables did not normalize by 12 weeks of training in women who had had preeclampsia.

CONCLUSION

This study demonstrates that exercise training in women who had had preeclampsia and control subjects improves components of MetS, endothelial function, vascular wall thickness, and autonomic control. Nonetheless, trained women who had had preeclampsia only reached a cardiovascular status that is comparable with sedentary healthy control subjects.

Retrograde shear rate in formerly preeclamptic and healthy women before and after exercise training: relationship with endothelial function

Blood flow patterns in conduit arteries characterized by high levels of retrograde shear stress can be detrimental for vascular health. In this study we examined whether retrograde shear rate and endothelial function are related in healthy and formerly preeclamptic (PE) women and whether this relationship is altered by exercise training. Formerly PE women (32 ± 4 yr, n = 20) and controls (32 ± 4 yr, n = 20), all 6-12 mo postpartum, performed 12-wk aerobic exercise training. We measured brachial artery shear rate (SR) and endothelial function by flow-mediated dilation (FMD, echo-Doppler). We additionally performed power spectral analysis of heart rate variability and calculated low-frequency/high-frequency (LF/HF) ratio. Antegrade SR was not different between groups, while retrograde SR was significantly higher and FMD% lower in PE women compared with controls (both P < 0.05). Retrograde shear correlated strongly with FMD% in PE women and controls (P < 0.05). LF/HF ratio inversely correlated with brachial artery retrograde SR and FMD% (both P < 0.05) in PE women and controls. Exercise training reduced retrograde shear, improved FMD%, and reduced LF/HF ratios similarly in both groups (all P < 0.05). Training-induced changes in retrograde SR correlated with changes in FMD% and LF/HF ratio. A higher brachial artery retrograde SR relates to lower brachial artery endothelial function, in both controls and formerly PE women. Exercise training improves retrograde SR, while the magnitude of this change correlated strongly with improvements in FMD and reductions in LF/HF ratio. Therefore, the impact of PE and exercise training on endothelial health may, at least partly, be related to retrograde shear rate.

Vagal withdrawal and sympathetic overactivity contribute to the genesis of early-onset pregnancy-induced hypertension

Objective. In this study, we have assessed sympathovagal imbalance (SVI) by spectral analysis of heart rate variability (HRV) that contributes to the genesis of early-onset PIH. Methods. Body mass index (BMI), basal heart rate (BHR), blood pressure (BP) and HRV indices such as LFnu, HFnu, LF-HF ratio, mean RR, SDNN and RMSSD were assessed in normal pregnant women (Control group) and pregnant women having risk factors for PIH (Study group) at all the trimesters pregnancy. Retrospectively, those who did not develop PIH (Study group I) were separated from those who developed PIH (Study group II). Study group II was subdivided into early-onset and late-onset PIH. Sympathovagal balance (LF-HF ratio) was correlated with BMI, BHR and BP. Results. LF-HF ratio was significantly high in study group II compared to study group I and control group, and in early-onset PIH group compared to the late-onset category at all the trimesters of pregnancy, which was significantly correlated with BHR and BP. Alteration in HFnu in early-onset category was more prominent than the alteration in LFnu. Conclusion. Though the SVI in PIH is contributed by both sympathetic overactivity and vagal withdrawal, especially in early-onset type, SVI is mainly due to vagal inhibition.

Spectral analysis of heart rate variability for early prediction of pregnancy-induced hypertension

The early prediction of pregnancy-induced hypertension (PIH), a common morbid disorder of pregnancy is unsatisfactory. Therefore, in the present study we have investigated the role of spectral analysis of heart rate variability (HRV) in the early prediction of PIH. Spectral analysis of HRV was performed in three groups of subjects (Group I: normal pregnant women; Group II: pregnant women with risk factors, but did not develop PIH; Group III: pregnant women with risk factors and developed PIH). It was observed that the LF-HF ratio, the most sensitive indicator of sympathovagal balance, was significantly high (p < 0.01) since early pregnancy in group III compared to other groups, which was significantly correlated with heart rate and blood pressure. It was suggested that the predictive knowledge of sympathovagal imbalance should be utilized in designing the prevention and management of PIH.

The relationship of plasma volume, sympathetic tone, and proinflammatory cytokines in young healthy nonpregnant women

OBJECTIVE

Preeclampsia has been associated with elevated proinflammatory markers, increased sympathetic activity, and decreased plasma volume (PV). We hypothesized that these associations would be identified in women prior to a first pregnancy.

METHODS

We studied 76 healthy nulligravid participants measuring the proinflammatory markers C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-alpha). Plasma volume was measured in supine position and corrected for body mass index (BMI). We examined supine plasma levels of epinephrine and norepinephrine and blood pressure response to Valsalva maneuver to quantify sympathetic activation. We then examined the association of PV and sympathetic activity with proinflammatory cytokines with P < .05 accepted for significance.

RESULTS

CRP was significantly increased in participants with lowest PV/BMI quartile when compared to middle 2 quartiles and highest quartile (analysis of variance [ANOVA], P = .037). We found no significant association of PV/BMI with either IL-6 or TNF-alpha. Both plasma epinephrine concentration (r = .29, P = .02) and the late phase II (phase II_L) blood pressure response to Valsalva maneuver (r = .44, P < .0001) were associated with serum IL-6 concentrations.

CONCLUSIONS

Low PV is associated with increased CRP levels and increased sympathetic tone is linked to elevated IL-6 concentration in young nonpregnant women. These findings represent elements of a nonpregnancy phenotype that parallels the findings observed in preeclampsia and in women at risk for ischemic cardiovascular disease. This suggests that the relationships observed during preeclampsia, which have been associated with placental pathology, may predate pregnancy and be independent of placental activity.

Sensitivity of Spontaneous Baroreflex Control of the Heart and Hemodynamic Parameters are Not Influenced by the Menstrual Cycle

OBJECTIVE

The purpose of this study was to evaluate if hemodynamic parameters and sympathetic activity vary between the follicular and luteal phase of the menstrual cycle before using sympathetic activity in pre-pregnancy risk assessment for preeclampsia.

METHODS

We studied 39 healthy women at days 5 to 10 and days 18 to 25 of the menstrual cycle. Blood pressure, heart rate, cardiac output, and total peripheral resistance were measured continuously using noninvasive finger arterial pressure waveform registration (Portapres Model 2, BMI, The Netherlands). Baroreflex sensitivity (BRS) and sympathetic activity by phase angle difference were studied using spectral analysis and xBRS.

RESULTS

There were no differences in hemodynamic parameters, BRS, and phase angle difference.

CONCLUSION

There is no difference in blood pressure, BRS, and sympathetic activity between the first and second half of the menstrual period. We recommend using the first half of the cycle to be certain that no pregnancy exists, as the influence of very early pregnancy is unknown.

HAEMODYNAMIC CONTRIBUTIONS TO THE PATHOGENESIS OF PREECLAMPSIA AND ECLAMPSIA

Current hypotheses regarding the origins of preeclampsia have focused on the “Two stage model”. This model suggests that the primary steps in the pathophysiologic sequence of preeclampsia are initiated by abnormal placentation including the classic finding of abnormal trophoblast invasion of maternal decidual spiral arteries. The second stage of the sequence includes the elaboration of a single or multiple substances from these disordered placentas which contribute to the generalized maternal systemic illness, eventually manifesting as endothelial injury, hypertension and proteinuria. Recent studies have focused on the role of pro and anti-angiogenic peptides as potential placentally derived aetiologic agents in this pathophysiologic sequence, although other placental products have been highlighted in recent research. Despite the fact that this modeling of preeclampsia has widespread support significant limitations to this hypothesis can be identified.

Orthostatic stress response during the menstrual cycle is unaltered in formerly preeclamptic women with low plasma volume

Plasma volume (PV) varies with the menstrual cycle not only in healthy parous controls (CON) but also in formerly preeclamptic women with a subnormal PV (LPV). It is unknown whether formerly preeclamptic women with LPV are more susceptible to orthostatic stress than healthy controls. In this study, the authors compared autonomic responses to acute (standing from supine position) and gradual (menstrual cycle) orthostatic stress between LPV and CON. In 11 LPV (PV<or= 49 mL/kg lean body mass) and 7 CON, beat-to-beat blood pressure (BP) and heart rate (HR) were measured in supine position and after an orthostatic stress test, during the follicular phase (FP) and luteal phase (LP) of the menstrual cycle. Spectral analysis (fast Fourier transform) was performed on beat-to-beat signals to quantify the magnitude of the spontaneous BP and pulse interval (PI) fluctuations. The absolute powers within the low-frequency (0.04-0.15 Hz) and high-frequency (0.15-0.4 Hz) ranges of BP and PI were used as estimates for sympathetic and parasympathetic activity, respectively. Baroreflex sensitivity was calculated as the transfer function gain from low-frequency systolic BP to PI. Differences between groups, menstrual phase, and response to standing were compared by analysis of variance. Basal BP was comparable in both study groups. However, basal PI and spontaneous baroreflex sensitivity were lower in LPV than in CON. The autonomic responses to acute and gradual orthostatic stress were similar in the 2 groups, irrespective of the phase of the menstrual cycle. The cardiovascular response to acute and gradual orthostatic stress in both FP and LP is comparable in LPV and CON.

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

OBJECTIVE

To test the hypothesis that during pre-eclampsia microvascular function and structure are disturbed, which contributes to raised venular resistance.

METHODS

The microcirculation of the skin and bulbar conjunctiva was studied in 11 women with preeclampsia and nine parous controls, both in the third trimester and 3 months postpartum. Using intravital videomicroscopy, arteriolar and venular diameters were determined in the conjunctiva. In addition, skin capillary densities and morphology were determined.

RESULTS

Conjunctival venular diameters were 30% smaller in pre-eclampsia compared with controls, both during pregnancy (P < 0.01) and postpartum (P = 0.045). Arteriolar diameters also tended to be smaller; however, this difference was not statistically significant. In women with pre-eclampsia we found a higher percentage of tortuous/dilated skin capillaries (5%) compared with controls (0%; P < 0.05). Three months postpartum, this difference had disappeared. Skin capillary densities did not differ between the groups.

CONCLUSION

Women with severe pre-eclampsia have narrow venules, both during manifest disease and postpartum. Possibly, these narrow venules raise venular resistance and with it, hydrostatic pressure in the capillary bed. The latter, in turn, may explain the higher number of tortuous/dilated capillaries in women with preeclampsia. These findings support an important role of the venous system in the pathogenesis of pre-eclampsia.