Blunted autonomic response to volume expansion in formerly preeclamptic women with low plasma volume.

Contains fulltext : 80636.pdf (publisher's version ) (Closed access)OBJECTIVE: We hypothesize that low plasma volume in normotensive formerly preeclamptic women reflects reduced venous storage capacity. To test this hypothesis, we compared circulatory and autonomic responses to acute volume loading between women with low and those with normal plasma volume. METHODS: In 24 normotensive formerly preeclamptic women at least 6 months postpartum, we administered 500 mL of iso-oncotic fluid by constant intravenous infusion in 30 minutes, while recording changes in heart rate, blood pressure, cardiac output, and measuring active plasma renin and alpha-atrial natriuretic peptide concentrations. We estimated arterial sympathetic control, cardiac autonomic regulatory balance, and baroreflex sensitivity using spectral analysis. Intergroup and intragroup changes were analyzed nonparametrically. RESULTS: 17 women (71%) had low plasma volume and 7 (29%) had normal plasma volume. Plasma volume expansion induced comparable changes in blood pressure, heart rate, baroreflex sensitivity, and active plasma renin concentration in low plasma volume and normal plasma volume. Cardiac output and alpha-atrial natriuretic peptide increased in low plasma volume but not in normal plasma volume. Volume expansion reduced sympathetic activity ( from 2.41 to 1.76 mm Hg(2), P = .03) in normal plasma volume but not in low plasma volume ( from 2.72 to 2.48 mm Hg(2), P > .05). CONCLUSION: The sympathoinhibitory response to volume expansion is diminished in low plasma volume, which suggests that cardiovascular reflex function is impaired. We speculate that this defect contributes to circulatory maladaptation to pregnancy, sympathetic dominance, and the development of gestational hypertensive disease

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

Contains fulltext : 51858.pdf (publisher's version ) (Closed access)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

Maternal nonpregnant vascular function correlates with subsequent fetal growth.

Contains fulltext : 48774.pdf (publisher's version ) (Closed access)OBJECTIVE: Evidence is accumulating that fetal growth is influenced by preexisting maternal disorder(s) hampering endothelial function. We tested the hypothesis that in nonpregnant normotensive, formerly preeclamptic women, vascular function predicts the development of fetal growth restriction. METHODS: In 60 formerly preeclamptic women, we measured central hemodynamic and vascular and clotting function mid follicular phase during the menstrual cycle. Inclusion for final analysis required besides normotension, a subsequent singleton pregnancy, established within 1 year after the prepregnant evaluation and ongoing beyond 16 weeks' gestation. In the ongoing pregnancy we determined birth weight and birth weight percentile. RESULTS: Among 60 formerly preeclamptic women, 45 (75%) were normotensive. Thirty-one (69%) participants succeeded in establishing an ongoing pregnancy within 1 year and were included for final analysis. Of the 31 subsequent pregnancies, 8 (26%) were complicated by fetal growth restriction. Prepregnant left and right uterine artery pulsatility index (PI) correlated inversely with carotid artery compliance ( r = 0.57, P = .005, r = 0.62, P = .002) and venous compliance ( r = 0.49, P = .02 and r = 0.45, P = .04, respectively). The latter, in turn, correlates with plasma volume ( r = 0.63, P = .001) and total peripheral vascular resistance index ( r = -0.45, P = .02). Finally, prepregnant left and right uterine artery PI correlated inversely with subsequent achieved fetal growth ( r = -0.68, P < .0001 and r = -0.58, P = .001, respectively). CONCLUSION: In nonpregnant normotensive, formerly preeclamptic women, an elevated uterine artery PI predisposes to subsequent restriction in fetal growth

Low plasma volume coincides with sympathetic hyperactivity and reduced baroreflex sensitivity in formerly preeclamptic patients.

Contains fulltext : 50660.pdf (publisher's version ) (Open Access)BACKGROUND: Preeclampsia is associated with enhanced sympathetic activity as well as subnormal plasma volume. Meanwhile, in over 50% of these complicated pregnancies, the subnormal plasma volume has been found to persist for a prolonged period after pregnancy. The objective of this study is to test the hypothesis that in normotensive formerly-preeclamptic women, persistence of a subnormal plasma volume coincides with enhanced sympathetic activity and with it, an altered autonomic control of blood pressure. METHODS: Forty-eight formerly-preeclamptic women participated in this study. After measurement of their plasma volume by iodine 125-albumin indicator dilution, they were subdivided into a group with a normal plasma volume (plasma volume > 48 ml/kg lean body mass) and a group with a subnormal plasma volume (< or = 48 ml/kg lean body mass). We performed spectral analysis on their beat-to-beat blood pressure and heart rate recordings and compared both groups using non-parametric tests. RESULTS: Formerly-preeclamptic women with a subnormal plasma volume had a higher sympathetic activity (P = .001) and a lower baroreflex sensitivity (P = .04) than their counterparts with a normal plasma volume. CONCLUSION: In normotensive formerly-preeclamptic women, a subnormal plasma volume coincides with a higher sympathetic activity in the blood pressure regulation and lower baroreflex sensitivity. Whether these alterations in the autonomic control mechanisms are a cause or effect of the subnormal plasma volume remains to be elucidated

A subnormal plasma volume in formerly preeclamptic women is associated with a low venous capacitance.

Contains fulltext : 48810.pdf (publisher's version ) (Open Access)OBJECTIVE: Pregnancy induces a smaller rise in plasma volume in formerly preeclamptic women with a pre-existent subnormal plasma volume than in their counterparts with a normal plasma volume. These women also have a three times higher recurrence rate of pregnancy-induced hypertensive disorders. In this study we tested the hypothesis that a subnormal plasma volume in these women is related to a lower capacitance of their venous compartment. METHODS: In 31 nonpregnant formerly preeclamptic women with a subnormal plasma volume and eight parous controls, we infused intravenously 500 mL of a modified gelatin solution over 30 minutes. Before and after infusion we measured the circulating levels of alpha-atrial natriuretic peptide (alpha-ANP) and active plasma renin concentration (APRC). During volume loading, we recorded the change in heart rate, stroke volume, and cardiac output using pulse contour analysis. We measured the ratio of percent change in blood volume and percent change in cardiac output during volume loading as a marker for venous capacitance. RESULTS: During volume loading, patients differed from controls by a larger rise in alpha-ANP, pulse rate, and cardiac output, and by a lower estimated venous capacitance. The concomitant response of stroke volume and APRC did not differ appreciably between groups. CONCLUSION: Formerly preeclamptic women with a subnormal plasma volume differ from controls with a normal plasma volume by a reduced venous capacitance. These results support our hypothesis that, in these women, a subnormal plasma volume indicates the presence of a subnormal venous capacitance