A methodology for examining the association between plasma volume and micronutrient biomarker mass and concentration in healthy eumenorrheic women

Background

Accurate estimation and interpretation of nutritional biomarker concentrations are important in nutritional research, clinical care, and public health surveillance. Plasma volume (PV) may affect the interpretation of plasma biomarkers but is rarely measured. We aimed to examine the association between plasma volume (PV) and micronutrient biomarker concentrations and mass as part of pilot work to develop methods.

Methods

Nine healthy women with regular menstrual cycles provided fasting blood samples to measure micronutrient biomarkers. Indocyanine green was injected, and five timed blood draws were taken from 2 to 5 min to measure PV. Visits were scheduled around menstrual cycle day 2. Retinol, 25-hydroxyvitamin D, riboflavin, alpha-tocopherol, zinc, copper, magnesium, manganese, cobalt, iron, and ferritin concentrations were measured in serum. Total circulating micronutrient biomarker mass was calculated from PV and concentration.

Results

The mean PV was 2067 ±  470 mL. PV correlated positively with concentration of iron (r = 0.87, P = 0.005); other correlations were weaker with p > 0.05. PV and total mass of retinol (r = 0.90), 25(OH)D (r = 0.75), zinc (r = 0.88), copper (r = 0.83), magnesium (r = 0.93), manganese (r = 0.72), and iron (r = 0.92) were strongly correlated (all p < 0.05). PV was positively correlated with circulating micronutrient mass for most biomarkers, implying that concentrations are maintained at different volumes of plasma. Larger studies are needed to further examine these relationships.

Conclusion

Though there appear to be some association between micronutrient biomarker mass and plasma volume, we are unable to draw a firm conclusion about any relationship from these results because of the small sample size. We consider these findings as a preliminary analysis to establish methods for future studies.

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.

Detection of early left ventricular dysfunction in patients with maternal placental syndrome using tissue Doppler and strain rate imaging

BACKGROUND

Maternal placental syndromes (MPS) occur as a consequence of abnormal placental vessel formation and refer to hypertensive pregnancy disorders and related placental abnormalities. The aim of this study is to investigate early alterations in left ventricular function in patients with history of MPS using tissue Doppler and strain rate imaging.

METHODS

We enrolled 122 females who were 6 months after delivery. Group 1 included 72 patients who experienced MPS. Group 2 included 50 women with normal pregnancy as control.

RESULTS

There was no significant difference between both groups with regard to ejection fraction, deceleration time, isovolumetric relaxation time, or E/A ratio. Deterioration of left ventricular systolic and diastolic function was evident in the MPS group, by TDI parameters (significantly lower values of Sm 7.5 ± 1.2 vs. 9.1 ± 1.3, p < 0.001; Em 7.0 ± 0.8 vs. 10.0 ± 1.4, p = 0.02; and Em-to-Am ratio 0.84 ± 0.14 vs. 1.2 ± 0.18, p < 0.001). Systolic strain, peak systolic strain rate, and early and late diastolic strain rates were also significantly lower in patients who had MPS than in the control group (-18.7 ± 2.6 vs. -20.8 ± 1.5, p < 0.001; -0.92 ± 0.14 vs. -1.01 ± 0.23, p < 0.001; 1.05 ± 0.11 vs. 1.29 ± 0.24, p < 0.001; 1.8 ± 0.3 vs. 1.2 ± 0.4, p < 0.001, respectively) and in patients who had severe pre-eclampia than mild pre-eclampsia. Pre-eclamptic women who had preterm delivery showed significantly higher left diastolic dysfunction.

CONCLUSION

Left ventricular systolic and diastolic dysfunction occur in patients with history of MPS. These abnormalities are evident on tissue Doppler and strain imaging even in the absence of changes in ejection fraction or standard diastolic parameters.

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.

Asian women have attenuated sympathetic activation but enhanced renal-adrenal responses during pregnancy compared to Caucasian women

Asians have a lower prevalence of hypertensive disorders of pregnancy than Caucasians. Since sympathetic overactivity and dysregulation of the renal-adrenal system (e.g. low aldosterone levels) have been found in preeclamptic women, we hypothesized that Asians have lower muscle sympathetic nerve activity (MSNA) and greater aldosterone concentrations during normal pregnancy than Caucasians. In a prospective study, blood pressure (BP), heart rate (HR), and MSNA were measured during supine and upright tilt (30 deg and 60 deg for 5 min each) in 9 Asians (32 ± 1 years (mean ± SEM)) and 12 Caucasians (29 ± 1 years) during pre-, early (≤8 weeks of gestation) and late (32-36 weeks) pregnancy, and post-partum (6-10 weeks after delivery). Supine MSNA increased with pregnancy in both groups (P < 0.001); it was significantly lower in Asians than Caucasians (14 ± 3 vs. 23 ± 3 bursts min(-1) and 16 ± 5 vs. 30 ± 3 bursts min(-1) in early and late pregnancy, respectively; P = 0.023). BP decreased during early pregnancy (P < 0.001), but was restored during late pregnancy. HR increased during pregnancy (P < 0.001) with no racial difference (P = 0.758). MSNA increased during tilting and it was markedly lower in Asians than Caucasians in late pregnancy (31 ± 6 vs. 49 ± 3 bursts min(-1) at 60 deg tilt; P = 0.003). Upright BP was lower in Asians, even in pre-pregnancy (P = 0.006), and this racial difference persisted during pregnancy. Direct renin and aldosterone increased during pregnancy (both P < 0.001); these hormones were greater in Asians (P = 0.086 and P = 0.014). Thus, Asians have less sympathetic activation but more upregulated renal-adrenal responses than Caucasians during pregnancy. These results may explain, at least in part, why Asian women are at low risk of hypertensive disorders in pregnancy.

Increased B-type natriuretic peptide levels in early-onset versus late-onset preeclampsia

BACKGROUND

We compared B-type natriuretic peptide (BNP) levels, clinical and laboratory findings in early-onset preeclampsia (EOP), late-onset preeclampsia (LOP) and healthy pregnant groups.

METHODS

We studied 40 healthy pregnant and 40 preeclamptic patients. Preeclamptics were divided in two groups, the EOP group (n=20) and LOP group (n=20), according to gestational age at the onset of disease. The distinction criterion for early- vs. late-onset was set as week 34 of gestation. The concentration of the BNP levels was measured by a sandwich fluorescence immunoassay. For statistical analysis of the clinical and laboratory findings non-parametric methods were applied.

RESULTS

BNP levels were higher in EOP [61.35 (36.95-93.25) pg/mL] and LOP patients [32.4 (19.15-39.2) pg/mL] than in healthy pregnant women [10.05 (6.08-16.03) pg/mL] (both p<0.001). Furthermore, EOPs had significantly higher BNP levels as compared to LOP patients (p<0.001). A BNP cut-off <24.5 pg/mL had a negative-predictive value of 85.1% excluding preeclampsia. There was a significant inverse correlation between plasma BNP levels of EOP patients and sodium (p<0.05) and total protein concentrations (p<0.05). In the EOP group, a significant positive correlation was observed between plasma levels of BNP and hematocrit (p<0.05), serum potassium (p<0.05), urea (p<0.05) and 24-h proteinuria (p<0.05).

CONCLUSIONS

BNP levels were significantly higher in EOP than in LOP patients. The cut-off value <24.5 pg/mL seems to be a powerful discriminative indicator excluding preeclampsia. The amount of proteinuria and total protein levels correlate with the elevation of the BNP levels. In EOP the extent of proteinuria is higher than in the LOP.

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.

Pulse pressure and arterial compliance prior to pregnancy and the development of complicated hypertension during pregnancy

We examined the relationship between prepregnant pulse pressure (PP), mean arterial pressure (MAP), cardiac output (CO)/PP, a measure of arterial compliance, and development of complicated hypertension (CH) during pregnancy with the goal of identifying a potential predictor of CH. Twenty nulliparous participants were studied before pregnancy; 17 had normal pregnancies (control; CTL) and 3 CH. Blood pressure monitoring was performed using tonometry. Cardiac output was determined by Doppler echocardiograph. Data are expressed as mean +/- SD. Prepregnant PP was significantly higher in CH participants (CH: 58.3 +/- 6.3, CTL: 46.2 +/- 1.7 mm Hg; P = .02). Cardiac output /pulse pressure was significantly lower in CH participants (CH: 6.9 +/- 1.8, CTL: 10.6 +/- 2.8; P = .04). Mean arterial pressure was not significantly different. Increased PP before pregnancy may suggest increased risk for CH. With accurate prediction of CH before pregnancy, initiation of preventative measures could begin earlier, either prior to or in early pregnancy, potentially increasing preventative efficacy and decreasing CH.