Cardiac output and related haemodynamics during pregnancy: a series of meta-analyses

Influence of maternal characteristics and gestational age on hemodynamic indices: NICOM device-specific reference ranges

OBJECTIVES

To construct reference ranges for stroke volume, cardiac output and systemic vascular resistance (SVR) in normal pregnancy for the NICOM® device, and to explore associations between maternal characteristics and these hemodynamic variables.

METHODS

This was a prospective cohort study of healthy singleton pregnancies between 10 and 40 weeks' gestation attending a tertiary referral hospital between September 2012 and May 2018. Measurements of stroke volume, cardiac output and SVR were obtained throughout pregnancy using NICOM, a non-invasive device based on bioreactance technology. NICOM device-specific reference ranges were created with respect to gestational age and maternal characteristics. Once the distribution of the data had been determined with respect to the gestational age, patient characteristics were added to the model to test whether they provided a significant improvement in prediction of the median value. The effect was assessed of maternal weight, height, smoking status, conception using assisted reproductive technology, nulliparity and ethnicity.

RESULTS

We included 411 women in this study. The relationships between cardiac variables and gestational age observed in the NICOM-specific reference ranges are consistent with previous findings, with increasing cardiac output values until around 35 weeks and a decrease thereafter until term, and decreasing SVR until around 36 weeks, followed by an increase towards 40 weeks. Stroke volume showed a small linear increase across gestation with lower variability in observations close to term. Maternal weight, height and age were associated with cardiac output (all P < 0.05) and SVR (all P < 0.01), whilst maternal weight and height were associated with stroke volume (both P < 0.001). Ethnicity was significantly associated with stroke volume (P = 0.001) but not with cardiac output or SVR.

CONCLUSIONS

This study presents device-specific reference ranges for stroke volume, cardiac output and SVR for the NICOM device in healthy pregnancy and describes the maternal characteristics that are associated with the values of these hemodynamic measurements. Studies using NICOM in pregnancy can use these ranges in order to evaluate observations relative to those expected in uncomplicated pregnancy conditional on maternal characteristics. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Left Ventricular Diastolic Function During the Normal Peripartum Period

BACKGROUND

Because cardiovascular function and hemodynamics markedly change during pregnancy, our aim was to elucidate left ventricular (LV) diastolic function in pregnant women.Methods and Results:We prospectively collected the data of 397 pregnant women treated between 2012 and 2013. We evaluated their LV systolic and diastolic functions via echocardiography during the 3rd trimester (28-30 weeks' gestation) and within 4 days of delivery. Additionally, we analyzed the cardiac geometry: relative wall thickness and LV mass index (LVMI). Diastolic dysfunction was defined as early diastolic mitral annulus velocity (e') <7 cm/s and peak early filling velocity (E)/e' ratio >15. The pregnant women were 33.7±5.0 years old and the prevalence of hypertensive disorders in pregnancy (HDP) was 4.0%. LV systolic function was preserved in all pregnant women. However, diastolic function significantly decreased after delivery (mean e': 12.6 vs. 11.6 cm/s, P<0.0001; median E/e' ratio: 6.4 vs. 7.3, P<0.0001). Diastolic function after delivery was associated with the prevalence of HDP (P=0.035) and was correlated with age (R=-0.17, P=0.0009) and LVMI (R=-0.30, P<0.0001). However, these changes in diastolic function remained within the normal range and only 1 woman (1/397, 0.3%) had LV diastolic dysfunction after delivery.

CONCLUSIONS

LV diastolic function decreased after delivery in pregnant women but was within the normal range.

The effect of parity on longitudinal maternal hemodynamics

BACKGROUND

Parous women have a lower risk for pregnancy complications, such as preeclampsia or delivery of small-for-gestational-age neonates. However, parous women are a heterogeneous group of patients because they contain a low-risk cohort with previously uncomplicated pregnancies and a high-risk cohort with previous pregnancies complicated by preeclampsia and/or small for gestational age. Previous studies examining the effect of parity on maternal hemodynamics, including cardiac output and peripheral vascular resistance, did not distinguish between parous women with and without a history of preeclampsia or small for gestational age and reported contradictory results.

OBJECTIVE

The objective of the study was to compare maternal hemodynamics in nulliparous women and in parous women with and without previous preeclampsia and/or small for gestational age.

STUDY DESIGN

This was a prospective, longitudinal study of maternal hemodynamics, assessed by a bioreactance method, measured at 11⁺⁰ to 13⁺⁶, 19⁺⁰ to 24⁺⁰, 30⁺⁰ to 34⁺⁰, and 35⁺⁰ to 37⁺⁰ weeks' gestation in 3 groups of women. Group 1 was composed of parous women without a history of preeclampsia and/or small for gestational age (n = 632), group 2 was composed of nulliparous women (n = 829), and group 3 was composed of parous women with a history of preeclampsia and/or small for gestational age (n = 113). A multilevel linear mixed-effects model was performed to compare the repeated measures of hemodynamic variables controlling for maternal characteristics, medical history, and development of preeclampsia or small for gestational age in the current pregnancy.

RESULTS

In groups 1 and 2, cardiac output increased with gestational age to a peak at 32 weeks and peripheral vascular resistance showed a reversed pattern with its nadir at 32 weeks; in group 1, compared with group 2, there was better cardiac adaptation, reflected in higher cardiac output and lower peripheral vascular resistance. In group 3 there was a hyperdynamic profile of higher cardiac output and lower peripheral vascular resistance at the first trimester followed by an earlier sharp decline of cardiac output and increase of peripheral vascular resistance from midgestation. The incidence of preeclampsia and small for gestational age was highest in group 3 and lowest in group 1.

CONCLUSION

There are parity-specific differences in maternal cardiac adaptation in pregnancy.

Left ventricular mechanics in late second trimester of healthy pregnancy

OBJECTIVE

To evaluate left ventricular (LV) mechanics in the second trimester of healthy pregnancy and to determine the influence of underpinning hemodynamics (heart rate (HR), preload and afterload) on LV mechanics during gestation.

METHODS

This was a cross-sectional study of 18 non-pregnant, 14 nulliparous pregnant (22-26 weeks' gestation) and 13 primiparous postpartum (12-16 weeks after delivery) women. All pregnant and postpartum women had uncomplicated, singleton gestations. Cardiac structure and function were assessed using echocardiography. LV mechanics, specifically longitudinal strain, circumferential strain and twist/untwist, were measured using speckle-tracking echocardiography. Differences between groups were identified using ANCOVA, with age, HR, end-diastolic volume (EDV) and systolic blood pressure (SBP) as covariates. Relationships between LV mechanics and hemodynamics were examined using Pearson's correlation.

RESULTS

There were no significant differences in LV structure and traditional measurements of systolic and diastolic function between the three groups. Pregnant women, compared with non-pregnant ones, had significantly higher resting longitudinal strain (-22 ± 2% vs -17 ± 3%; P = 0.002) and basal circumferential strain (-23 ± 4% vs -16 ± 2%; P = 0.001). Apical circumferential strain and LV twist and untwist mechanics were similar between the three groups. No statistically significant relationships were observed between LV mechanics and HR, EDV or SBP within the groups.

CONCLUSIONS

Compared to the non-pregnant state, pregnant women in the second trimester of a healthy pregnancy have significantly greater resting systolic function, as assessed by LV longitudinal and circumferential strain. Contrary to previous work, these data show that healthy pregnant women should not exhibit reductions in resting systolic function between 22 and 26 weeks' gestation. The enhanced myocardial contractile function during gestation does not appear to be related to hemodynamic load and could be the result of other physiological adaptations to pregnancy. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Sepsis in Pregnancy: Recognition and Resuscitation

The normal physiologic changes of pregnancy complicate evaluation for sepsis and subsequent management. Previous sepsis studies have specifically excluded pregnant patients. This narrative review evaluates the presentation, scoring systems for risk stratification, diagnosis, and management of sepsis in pregnancy. Sepsis is potentially fatal, but literature for the evaluation and treatment of this condition in pregnancy is scarce. While the definition and considerations of sepsis have changed with large, randomized controlled trials, pregnancy has consistently been among the exclusion criteria. The two pregnancy-specific sepsis scoring systems, the modified obstetric early warning scoring system (MOEWS) and Sepsis in Obstetrics Score (SOS), present a number of limitations for application in the emergency department (ED) setting. Methods of generation and subsequently limited validation leave significant gaps in identification of septic pregnant patients. Management requires consideration of a variety of sources in the septic pregnant patient. The underlying physiologic nature of pregnancy also highlights the need to individualize resuscitation and critical care efforts in this unique patient population. Pregnant septic patients require specific considerations and treatment goals to provide optimal care for this particular population. Guidelines and scoring systems currently exist, but further studies are required.

Energy Intake Requirements in Pregnancy

Energy intake requirements in pregnancy match the demands of resting metabolism, physical activity, and tissue growth. Energy balance in pregnancy is, therefore, defined as energy intake equal to energy expenditure plus energy storage. A detailed understanding of these components and their changes throughout gestation can inform energy intake recommendations for minimizing the risk of poor pregnancy outcomes. Energy expenditure is the sum of resting and physical activity-related expenditure. Resting metabolic rate increases during pregnancy as a result of increased body mass, pregnancy-associated physiological changes, i.e., cardiac output, and the growing fetus. Physical activity is extremely variable between women and may change over the course of pregnancy. The requirement for energy storage depends on maternal pregravid body size. For optimal pregnancy outcomes, women with low body weight require more fat mass accumulation than women with obesity, who do not require to accumulate fat mass at all. Given the high energy density of fat mass, these differences affect energy intake requirements for a healthy pregnancy greatly. In contrast, the energy stored in fetal and placental tissues is comparable between all women and have small impact on energy requirements. Different prediction equations have been developed to quantify energy intake requirements and we provide a brief review of the strengths and weaknesses and discuss their application for healthy management of weight gain in pregnant women.

Cardiac output measurements during high-risk Cesarean section using electrical bioreactance or arterial waveform analysis: assessment of agreement

OBJECTIVE

Maternal hemodynamics change significantly during Cesarean section complicated by massive hemorrhage or severe hypertensive disease. Cardiac output (CO) monitoring aids early, goal-directed hemodynamic therapy. The aim of this study was to record hemodynamic changes observed during Cesarean section in pregnancies at high risk of hemodynamic instability, using invasive (LiDCOrapid™) and non-invasive (NICOM®) devices, and to assess agreement between the two devices in measuring CO.

METHODS

Simultaneous intraoperative hemodynamic measurements were taken using the LiDCOrapid and NICOM devices, following standardized techniques, in women at high risk of hemodynamic instability undergoing Cesarean section. Agreement in CO measurements between the two devices was assessed using Bland-Altman plots and the agreement:tolerability index (ATI). Agreement analyses were performed for repeated measures in subjects, using centiles.

RESULTS

From 10 women, 307 paired measurements were analyzed. Mean bias (defined as the mean difference in CO measurements between the LiDCOrapid and NICOM devices) was 3.05 (95% CI, 1.89 to 4.21) L/min. Limits of agreement ranged from -1.58 (95% CI, -4.47 to -0.14) to 7.68 (95% CI, 6.24 to 10.56) L/min. The resulting agreement interval was 9.26 L/min which returned an ATI of 2.3.

CONCLUSIONS

There are large mean differences between CO measurements obtained during Cesarean section using the LiDCOrapid and NICOM hemodynamic monitors in pregnant women at high risk of hemodynamic instability, indicating that they should not be considered interchangeable clinically. There is an unacceptably low level of agreement (ATI > 2) in CO measurements between the devices, conferring a high risk of clinical misclassification during massive hemorrhage. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Novel collaborative cardiology and maternal fetal medicine practice - experience at the heart and pregnancy program

PURPOSE

The Heart and Pregnancy Program (HPP) was created to evaluate and manage pregnant women with cardiac conditions simultaneously by cardiology and maternal-fetal medicine (MFM). The objective of our study was to describe the experience at this multidisciplinary program.

METHODS

This is a retrospective review of women managed at HPP for over 4.5 years. Subjects were compared based on indication for referral.

RESULTS

One hundred and seventy-three women were seen during the time period. Referral indications included cardiac complaints without history of cardiac disease (n = 49, 28.3%), known cardiac disease (n = 96, 55.5%), and other high-risk conditions (n = 28, 16.2%). Those with a known history of cardiac disease were significantly more likely to be nulliparous, and those referred for other high-risk conditions were significantly more likely to be obese. Most women underwent echocardiography (n = 137, 79.2%). For the 140 women who delivered at our hospital, the average gestational age at delivery was 38.8 weeks and the Cesarean rate was 41.4% (n = 58). No significant adverse perinatal outcomes were noted.

CONCLUSIONS

In our collaborative cardiology/MFM practice, most pregnant women had known cardiac disease. No significant adverse outcomes were noted. Our experience provides support for creating a joint model of care for pregnant women with cardiac disease.

Preeclampsia: The Relationship between Uterine Artery Blood Flow and Trophoblast Function

Maternal uterine artery blood flow is critical to maintaining the intrauterine environment, permitting normal placental function, and supporting fetal growth. It has long been believed that inadequate transformation of the maternal uterine vasculature is a consequence of primary defective trophoblast invasion and leads to the development of preeclampsia. That early pregnancy maternal uterine artery perfusion is strongly associated with placental cellular function and behaviour has always been interpreted in this context. Consistently observed changes in pre-conceptual maternal and uterine artery blood flow, abdominal pregnancy implantation, and late pregnancy have been challenging this concept, and suggest that abnormal placental perfusion may result in trophoblast impairment, rather than the other way round. This review focuses on evidence that maternal cardiovascular function plays a significant role in the pathophysiology of preeclampsia.

Maternal hemodynamics in screen-positive and screen-negative women of the ASPRE trial

OBJECTIVE

To compare maternal hemodynamics and perinatal outcome, in pregnancies that do not develop pre-eclampsia (PE) or deliver a small-for-gestational-age (SGA) neonate, between those identified at 11-13 weeks' gestation as being screen positive or negative for preterm PE, by a combination of maternal factors, mean arterial pressure, uterine artery pulsatility index, serum placental growth factor and pregnancy associated plasma protein-A.

METHODS

This was a prospective longitudinal cohort study of maternal cardiovascular function, assessed using a bioreactance method, in women undergoing first-trimester screening for PE. Maternal hemodynamics and perinatal outcome were compared between screen-positive and screen-negative women who did not have a medical comorbidity, did not develop PE or pregnancy-induced hypertension and delivered at term a live neonate with birth weight between the 5^th and 95^th percentiles. A multilevel linear mixed-effects model was used to compare the repeated measures of cardiac variables, controlling for maternal characteristics.

RESULTS

The screen-negative group (n = 926) had normal cardiac function changes across gestation, whereas the screen-positive group (n = 170) demonstrated static or reduced cardiac output and stroke volume and higher mean arterial pressure and peripheral vascular resistance with advancing gestation. In the screen-positive group, compared with screen-negative women, birth-weight Z-score was shifted toward lower values, with prevalence of delivery of a neonate below the 35^th , 30^th or 25^th percentile being about 70% higher, and the rate of operative delivery for fetal distress in labor also being higher.

CONCLUSION

Women who were screen positive for impaired placentation, even though they did not develop PE or deliver a SGA neonate, had pathological cardiac adaptation in pregnancy and increased risk of adverse perinatal outcome. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Methods and considerations concerning cardiac output measurement in pregnant women: recommendations of the International Working Group on Maternal Hemodynamics

Cardiac output (CO), along with blood pressure and vascular resistance, is one of the most important parameters of maternal hemodynamic function. Substantial changes in CO occur in normal pregnancy and in most obstetric complications. With the development of several non-invasive techniques for the measurement of CO, there is a growing interest in the determination of this parameter in pregnancy. These techniques were initially developed for use in critical-care settings and were subsequently adopted in obstetrics, often without appropriate validation for use in pregnancy. In this article, methods and devices for the measurement of CO are described and compared, and recommendations are formulated for their use in pregnancy, with the aim of standardizing the assessment of CO and peripheral vascular resistance in clinical practice and research studies on maternal hemodynamics. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Correlation between central and uterine hemodynamics in hypertensive disorders of pregnancy

OBJECTIVE

Pregnancies affected by a hypertensive disorder (HDP) have increased uterine artery pulsatility index (UtA-PI) compared with that in healthy pregnancies. Women with HDP are also known to have lower cardiac output and increased systemic vascular resistance. The aim of this study was to investigate the relationship between central and uterine hemodynamics in HDP and uncomplicated pregnancy.

METHODS

This was a prospective study of HDP and normotensive control singleton pregnancies presenting at a tertiary referral hospital between January 2012 and December 2017. Paired measurements of maternal hemodynamics, using a non-invasive device (USCOM-1A®), and UtA-PI were performed in the third trimester. HDP pregnancies were divided into preterm (onset < 37 weeks' gestation) and term (onset ≥ 37 weeks). Spearman's rank coefficient was used to assess the correlation between the central and uteroplacental hemodynamics. Regression analysis was performed to assess the association of UtA-PI with independent variables.

RESULTS

We included 231 women with HDP (152 with preterm and 79 with term HDP) and 378 controls with normotensive pregnancy. Compared with controls, women with preterm HDP had significantly lower cardiac output (median (interquartile range (IQR)), 6.0 (5.1-7.2) vs 6.6 (5.8-7.5) L/min; P < 0.001) and significantly higher systemic vascular resistance (median (IQR), 1394 (1189-1670) vs 1063 (915-1222) dynes × s/cm⁵ ; P < 0.001) and UtA-PI (median (IQR), 1.0 (0.75-1.4) vs 0.67 (0.58-0.83); P < 0.001). Conversely, in women with term HDP, there were no significant differences in heart rate, cardiac output or UtA-PI compared with controls (all P > 0.05), while systemic vascular resistance was significantly higher (median (IQR), 1315 (1099-1527) vs 1063 (915-1222) dynes × s/cm⁵ ; P < 0.001). On multiple regression analysis, heart rate, mean arterial pressure and stroke volume were associated significantly with mean UtA-PI (all P < 0.001).

CONCLUSIONS

Differences observed between HDP and normotensive pregnancies in third-trimester UtA resistance are mirrored in the central maternal hemodynamic parameters. Late pregnancy differences in the uteroplacental circulation in preterm and term HDP are an index of maternal cardiovascular function rather than being related to inadequate spiral artery remodeling and impaired placentation. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Accuracy and precision of USCOM versus transthoracic echocardiography before and during pregnancy

OBJECTIVE

Monitoring hemodynamic status throughout pregnancy may help in identifying women with maladaptation predisposing to hypertensive complications. The Ultrasonic Cardiac Output Monitor (USCOM) is an easy-to-operate device for measuring cardiac output (CO) quickly. Our aim was to assess agreement between USCOM and transthoracic echocardiography (TTE) in: 1) non-pregnant women to correct for possible sources of discrepancy; 2) women longitudinally over the course of the pregnancy.

STUDY DESIGN

High-risk women admitted for cardiovascular risk factor evaluation before pregnancy and multiple times during pregnancy, were included. CO was measured by TTE directly followed by USCOM measurements.

MAIN OUTCOME MEASURES

Bias, limits of agreement (LOA) and percentage error between the two methods by Bland-Altman analysis.

RESULTS

Despite comparable non-pregnant CO levels (4.6 L/min), LOA and percentage error between the two methods improved moderately by optimizing the measurements using only the highest quality USCOM recordings in 132 non-pregnant women (percentage error of 39% and 30%, respectively). During pregnancy, in total 83, 106, 96 and 77 measurements were evaluated at respectively 12, 16, 20 and 30 weeks gestational age. Mean CO in USCOM was about 0.6 L/min higher compared to TTE in all trimesters; percentage error ranged from 35% to 45%. Linear mixed model analysis showed no association between bias and moment of measurement.

CONCLUSION

Agreement between USCOM and TTE in pregnancy was outside our a priori determined level of acceptability and therefore absolute values of USCOM and TTE cannot be used interchangeably. Future research should focus on the agreement of USCOM and TTE in clinical decision-making.

Hypertension in pregnancy: Pathophysiology and treatment

Hypertensive disorders of pregnancy, an umbrella term that includes preexisting and gestational hypertension, preeclampsia, and eclampsia, complicate up to 10% of pregnancies and represent a significant cause of maternal and perinatal morbidity and mortality. Despite the differences in guidelines, there appears to be consensus that severe hypertension and non-severe hypertension with evidence of end-organ damage need to be controlled; yet the ideal target ranges below 160/110 mmHg remain a source of debate. This review outlines the definition, pathophysiology, goals of therapy, and treatment agents used in hypertensive disorders of pregnancy.

Role of pregnancy hormones and hormonal interaction on the maternal cardiovascular system: a literature review

Hormones have a vital duty in the conservation of physiological cardiovascular function during pregnancy. Alterations in oestrogen, progesterone and prolactin levels are associated with changes in the cardiovascular system to support the growing foetus and counteract pregnancy stresses. Pregnancy hormones are, however, also linked to numerous pathophysiological outcomes on the cardiovascular system. The expression and effects of the three main pregnancy hormones (oestrogen, prolactin and progesterone) vary depending on the gestation period. However, the reaction of a target cell also depends on the abundance of hormone receptors and impacts put forth by other hormones. Hormonal interaction may be synergistic, antagonistic or permissive. It is crucial to explore the cross talk of pregnancy hormones during gestation, as this may have a greater impact on the overall changes to the cardiovascular system.

Factors associated with increased levels of brain natriuretic peptide and cardiac troponin I during the peripartum period

BACKGROUND

We aimed to investigate the values and the changes of brain natriuretic peptide (BNP) and cardiac troponin in pregnant women.

METHODS AND RESULTS

We prospectively collected the data of 405 pregnant women who were treated at Japanese general hospital between 2012 and 2013. We analyzed their laboratory data and echocardiographic findings during the third trimester (28-30 weeks' gestation) and within 4 days of delivery. In addition, we evaluated the factors associated with elevation of BNP and cardiac troponin I (cTnI) levels. The pregnant women were 33.8 ± 5.0 years old and the prevalence of pregnancy induced hypertension (PIH) and placental abnormality was 4.2% and 2.5%, respectively. BNP levels increased after delivery (13.2 pg/mL vs. 23.5 pg/mL; P <0.001), correlated with increased left ventricular diastolic dimension (P = 0.035), left atrial dimension (P <0.001), and decreased hemoglobin (P <0.001). Moreover, cTnI levels increased to over 0.015 ng/mL after delivery in 4.0% of pregnant women. In multivariate analysis, PIH (OR: 18.71, P = 0.003), placental abnormality (OR: 26.78, P = 0.007), and decreased hemoglobin after delivery (OR: 2.59, P <0.001) were the factors associated with elevated cTnI.

CONCLUSIONS

BNP levels increased in association with cardiac chamber enlargement and decreased hemoglobin after delivery. Additionally, the factors affecting elevated cTnI levels were related to labor and delivery.

Recognition and Management of Sepsis in the Obstetric Patient

Sepsis is one of the principal causes of maternal mortality in obstetrics. Physiologic changes that occur during pregnancy create a vulnerable environment, predisposing pregnant patients to the development of sepsis. Furthermore, these changes can mask sepsis indicators normally seen in the nonobstetric population, making it difficult to recognize and treat sepsis in a timely manner. The use of maternal-specific early warning tools for sepsis identification and knowledge of appropriate interventions and their effects on the mother and fetus can help clinicians obtain the best patient outcomes in acute care settings. This article outlines the signs and symptoms of sepsis in obstetric patients and discusses treatment options used in critical care settings.

Uterine and fetal placental Doppler indices are associated with maternal cardiovascular function

BACKGROUND

The mechanism underlying fetal-placental Doppler index changes in preeclampsia and/or fetal growth restriction are unknown, although both are associated with maternal cardiovascular dysfunction.

OBJECTIVE

We sought to investigate whether there was a relationship between maternal cardiac output and vascular resistance and fetoplacental Doppler findings in healthy and complicated pregnancy.

STUDY DESIGN

Women with healthy pregnancies (n=62), preeclamptic pregnancies (n=13), preeclamptic pregnancies with fetal growth restriction (n=15), or fetal growth restricted pregnancies (n=17) from 24-40 weeks gestation were included. All of them underwent measurement of cardiac output with the use of an inert gas rebreathing technique and derivation of peripheral vascular resistance. Uterine and fetal Doppler indices were recorded; the latter were z scored to account for gestation. Associations were determined by polynomial regression analyses.

RESULTS

Mean uterine artery pulsatility index was higher in fetal growth restriction (1.37; P=.026) and preeclampsia+fetal growth restriction (1.63; P=.001) but not preeclampsia (0.92; P=1) compared with control subjects (0.8). There was a negative relationship between uterine pulsatility index and cardiac output (r²=0.101; P=.025) and umbilical pulsatility index z score and cardiac output (r²=0.078; P=.0015), and there were positive associations between uterine pulsatility index and peripheral vascular resistance (r²=0.150; P=.003) and umbilical pulsatility index z score and peripheral vascular resistance (r²= 0.145; P=.001). There was no significant relationship between cardiac output and peripheral vascular resistance with cerebral Doppler indices.

CONCLUSION

Uterine artery Doppler change is abnormally elevated in fetal growth restriction with and without preeclampsia, but not in preeclampsia, which may explain the limited sensitivity of uterine artery Doppler changes for all these complications when considered in aggregate. Furthermore, impedance within fetoplacental arterial vessels is at least, in part, associated with maternal cardiovascular function. This relationship may have important implications for fetal surveillance and would inform therapeutic options in those pathologic pregnancy conditions currently, and perhaps erroneously, attributed purely to placental maldevelopment. Uterine and fetal placental Doppler indices are associated significantly with maternal cardiovascular function. The classic description of uterine and fetal Doppler changes being initiated by placental maldevelopment is a less plausible explanation for the pathogenesis of the conditions than that relating to maternal cardiovascular changes.

A data-driven model to study utero-ovarian blood flow physiology during pregnancy

In this paper, we describe a mathematical model of the cardiovascular system in human pregnancy. An automated, closed-loop 1D-0D modelling framework was developed, and we demonstrate its efficacy in (1) reproducing measured multi-variate cardiovascular variables (pulse pressure, total peripheral resistance and cardiac output) and (2) providing automated estimates of variables that have not been measured (uterine arterial and venous blood flow, pulse wave velocity, pulsatility index). This is the first model capable of estimating volumetric blood flow to the uterus via the utero-ovarian communicating arteries. It is also the first model capable of capturing wave propagation phenomena in the utero-ovarian circulation, which are important for the accurate estimation of arterial stiffness in contemporary obstetric practice. The model will provide a basis for future studies aiming to elucidate the physiological mechanisms underlying the dynamic properties (changing shapes) of vascular flow waveforms that are observed with advancing gestation. This in turn will facilitate the development of methods for the earlier detection of pathologies that have an influence on vascular structure and behaviour.

Cardiac output changes from prior to pregnancy to post partum using two non-invasive techniques

OBJECTIVES

We aimed to describe cardiac output (CO) trend from prepregnancy to post partum using an inert gas rebreathing (IGR) device and compare these measurements with those obtained by a pulse waveform analysis (PWA) technique, both cross-sectionally and longitudinally.

METHODS

Non-smoking healthy women, aged 18-44 years, with body mass index <35 were included in this prospective observational study. CO measurements were collected at different time points (prepregnancy, at four different gestational epochs and post partum) using IGR and PWA. A linear mixed model analysis tested whether the longitudinal change in CO differed between the techniques. Bland-Altman analysis and intraclass correlation coefficient (ICC) were used for cross-sectional and a four-quadrant plot for longitudinal comparisons.

RESULTS

Of the 413 participants, 69 had a complete longitudinal assessment throughout pregnancy. In this latter cohort, the maximum CO rise was seen at 15.2 weeks with IGR (+17.5% from prepregnancy) and at 10.4 weeks with PWA (+7.7% from prepregnancy). Trends differed significantly (p=0.0093). Cross-sectional analysis was performed in the whole population of 413 women: the mean CO was 6.14 L/min and 6.38 L/min for PWA and IGR, respectively, the percentage of error was 46% and the ICC was 0.348, with similar results at all separate time points. Longitudinal concordance was 64%.

CONCLUSIONS

Despite differences between devices, the maximum CO rise in healthy pregnancies is more modest and earlier than previously reported. The two methods of CO measurement do not agree closely and cannot be used interchangeably. Technique-specific reference ranges are needed before they can be applied in research and clinical settings.

Evaluation and Management of Maternal Congenital Heart Disease: A Review

Objective

Congenital heart defects represent the most common major congenital anomalies. The objective of this review was to define the most common forms of congenital heart disease (CHD) in pregnancy, outline preconception counseling, discuss the associated morbidity and mortality of each lesion, and review current recommendations for management of CHD in pregnancy.

Evidence Acquisition

A MEDLINE search of "congenital heart disease in pregnancy" and specific conditions in pregnancy including "ventricular septal defect," "atrial septal defect," "left outflow obstruction," "right outflow obstruction," "tetralogy of Fallot," and "transposition of the great vessels" was performed.

Results

The evidence included in the review contains 18 retrospective studies, 8 meta-analyses or systematic reviews or expert opinions, 5 case reports including surgical case reports, 2 prospective studies, and 2 clinical texts.

Conclusions

Given advances in surgical and medical management, women with a history of congenital cardiac defects are more frequently reaching childbearing age and requiring obstetric care. Many women with CHD can have successful pregnancies, although there are a few conditions that confer significant maternal risk, and pregnancy may even be contraindicated. Appropriate care for women with CHD requires a knowledge of cardiac physiology in pregnancy, the common lesions of CHD, and coordinated care from cardiology and maternal-fetal medicine specialists.

Mechanisms and Clinical Significance of Endothelial Dysfunction in High-Risk Pregnancies

The maternal cardiovascular system undergoes critical anatomic and functional adaptations to achieve a successful pregnancy outcome which, if disrupted, can result in complications that significantly affect maternal and fetal health. Complications that involve the maternal cardiovascular system are among the most common disorders of pregnancy, including gestational hypertension, preeclampsia, gestational diabetes, and impaired fetal growth. As a central feature, maternal endothelial dysfunction is hypothesized to play a predominant role in mediating the pathogenesis of these high-risk pregnancies, and as such, might proceed and precipitate the clinical presentation of these pregnancy disorders. Improving or normalizing maternal endothelial function in high-risk pregnancies might be an effective therapeutic strategy to ameliorate maternal and fetal clinical outcomes.

Maternal hemodynamics: a method to classify hypertensive disorders of pregnancy

BACKGROUND

The classification of hypertensive disorders of pregnancy is based on the time at the onset of hypertension, proteinuria, and other associated complications. Maternal hemodynamic interrogation in hypertensive disorders of pregnancy considers not only the peripheral blood pressure but also the entire cardiovascular system, and it might help to classify the different clinical phenotypes of this syndrome.

OBJECTIVE

This study aimed to examine cardiovascular parameters in a cohort of patients affected by hypertensive disorders of pregnancy according to the clinical phenotypes that prioritize fetoplacental characteristics and not the time at onset of hypertensive disorders of pregnancy.

STUDY DESIGN

At the fetal-maternal medicine unit of Ziekenhuis Oost-Limburg (Genk, Belgium), maternal cardiovascular parameters were obtained through impedance cardiography using a noninvasive continuous cardiac output monitor with the patients placed in a standing position. The patients were classified as pregnant women with hypertensive disorders of pregnancy who delivered appropriate- and small-for-gestational-age fetuses. Normotensive pregnant women with an appropriate-for-gestational-age fetus at delivery were enrolled as the control group. The possible impact of obesity (body mass index ≥30 kg/m²) on maternal hemodynamics was reassessed in the same groups.

RESULTS

Maternal age, parity, body mass index, and blood pressure were not significantly different between the hypertensive disorders of pregnancy/appropriate-for-gestational-age and hypertensive disorders of pregnancy/small-for-gestational-age groups. The mean uterine artery pulsatility index was significantly higher in the hypertensive disorders of pregnancy/small-for-gestational-age group. The cardiac output and cardiac index were significantly lower in the hypertensive disorders of pregnancy/small-for-gestational-age group (cardiac output 6.5 L/min, cardiac index 3.6) than in the hypertensive disorders of pregnancy/appropriate-for-gestational-age group (cardiac output 7.6 L/min, cardiac index 3.9) but not between the hypertensive disorders of pregnancy/appropriate-for-gestational-age and control groups (cardiac output 7.6 L/min, cardiac index 4.0). Total vascular resistance was significantly higher in the hypertensive disorders of pregnancy/small-for-gestational-age group than in the hypertensive disorders of pregnancy/appropriate-for-gestational-age group and the control group. All women with hypertensive disorders of pregnancy showed signs of central arterial dysfunction. The cardiovascular parameters were not influenced by gestational age at the onset of hypertensive disorders of pregnancy, and no difference was observed between the women with appropriate-for-gestational-age fetuses affected by preeclampsia or by gestational hypertension with appropriate-for-gestational-age fetuses. Women in the obese/hypertensive disorders of pregnancy/appropriate-for-gestational-age and obese/hypertensive disorders of pregnancy/small-for-gestational-age groups showed a significant increase in cardiac output, as well as significant changes in other parameters, compared with the nonobese/hypertensive disorders of pregnancy/appropriate-for-gestational-age and nonobese/hypertensive disorders of pregnancy/small-for-gestational-age groups.

CONCLUSION

Significantly low cardiac output and high total vascular resistance characterized the women with hypertensive disorders of pregnancy associated with small for gestational age due to placental insufficiency, independent of the gestational age at the onset of hypertension. The cardiovascular parameters were not significantly different in the women with appropriate-for-gestational-age or small-for-gestational-age fetuses affected by preeclampsia or gestational hypertension. These findings support the view that maternal hemodynamics may be a candidate diagnostic tool to identify hypertensive disorders in pregnancies associated with small-for-gestational-age fetuses. This additional tool matches other reported evidence provided by uterine Doppler velocimetry, low vascular growth factors in the first trimester, and placental pathology. Obesity is associated with a significantly higher cardiac output and outweighs other determinants of hemodynamics in pregnancy; therefore, in future studies on hypertensive disorders, obesity should be studied as an additional disease and not simply as a demographic characteristic.

Cardiac remodeling in normotensive pregnancy and in pregnancy complicated by hypertension: systematic review and meta-analysis

OBJECTIVE

The aim of this systematic review and meta-analysis was to describe comprehensively the pattern of cardiac remodeling during normotensive human singleton pregnancy and to compare it with that of pregnancy complicated by hypertension.

METHODS

We performed a meta-analysis of the current literature on cardiac remodeling during normotensive and complicated pregnancies. Literature was retrieved from PubMed (NCBI) and EMBASE (Ovid) databases. Included studies needed to report a reference measurement (matched non-pregnant control group, prepregnancy or postpartum) and measurements made during predetermined gestational-age intervals. Mean differences between reference and pregnancy data were calculated using the random-effects model described by DerSimonian and Laird.

RESULTS

Forty-eight studies were included in the meta-analysis, with publication dates ranging from 1977 to 2016. During normotensive pregnancy, most geometric indices started to increase in the second trimester. Left ventricular mass (LVM) increased by 28.36 (95% CI, 19.73-37.00) g (24%), and relative wall thickness (RWT) increased by 0.03 (95% CI, 0.02-0.05) (10%) compared with those in the reference group. During hypertensive pregnancy, LVM and RWT increased more than during normotensive pregnancy (92 (95% CI, 75.46-108.54) g (95%) and 0.14 (95% CI, 0.09-0.19) (56%), respectively).

CONCLUSIONS

During normotensive pregnancy, most cardiac geometric indices change from the second trimester onwards. Both LVM and RWT increase, by 20% and 10%, respectively, consistent with concentric rather than eccentric remodeling. Cardiac adaptation in hypertensive pregnancy deviates from that in healthy pregnancy by a greater change in LVM (95% increase from reference) and RWT (56% increase from reference). Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Maternal Responses to Aerobic Exercise in Pregnancy

Exercise is one of the most physiologically challenging stressors requiring the coordination of metabolic, respiratory, and cardiovascular responses to meet increased energy requirements of the working muscle. During pregnancy, all women without contraindication are encouraged to exercise as part of a healthy lifestyle. Pregnancy itself is associated with profound physiological adaptations to the maternal cardiovascular, respiratory, and metabolic systems, which serve to support the needs of the growing fetus. Therefore the physiological adaptations to exercise during pregnancy are more pronounced and critically important. This review provides an overview of our current understanding of the physiological adaptations to acute prenatal exercise.

The hemodynamic effects of pregnancy on the lower extremity venous system

OBJECTIVE

Pregnancy has significant effects on the lower extremity venous system. Increasing venous pressure and blood volume, in combination with reduced flow rates within the deep veins, predisposes pregnant women to both primary and secondary chronic venous insufficiency (CVI). This review article highlights the specific physiologic and hemodynamic changes that occur during pregnancy and examines the nonpharmacologic, pharmacologic, and invasive interventions that are appropriate for both prophylaxis and treatment of CVI and venous thromboembolism (VTE).

METHODS

This study is a review article of the key literature related to VTE and CVI in pregnancy.

RESULTS

Significant hemodynamic changes occur in the lower extremities during pregnancy. Although well documented and essential to fetal development, these changes can have a negative impact on the maternal lower extremity venous circulation. Consequences of pregnancy can result in venous disease only during pregnancy or, particularly in the multiparous patient, can progress to CVI. An abundance of literature and guidelines exist for the management of VTE during pregnancy; however, the quality and extent of literature based around the management of primary CVI during pregnancy are modest at best.

CONCLUSIONS

The physiologic changes throughout the arterial and venous systems during pregnancy are well documented. However, there is a paucity of data available to construct guidelines for care, particularly in the pregnant patient with symptomatic superficial venous insufficiency. Further investigation in the form of prospective randomized trials is required to establish appropriate guidelines for treatment.

Relevance of Haemodynamics in Treating Pre-eclampsia

Blood pressure is a way of describing the end result of changes in cardiac output, intravascular volume and peripheral resistance. It has certain advantages in that it is a reproducible and easily measured parameter, but in itself, it offers only a limited understanding of the underlying haemodynamics. In pregnancy, profound haemodynamic changes occur and in hypertensive diseases of pregnancy defining a condition by blood pressure alone risks missing the underlying cause. Partly, this has been a problem of ascribing the cause of hypertensive syndromes to the placenta which has inhibited rigorous research into other possible causes of haemodynamic dysfunction. It is becoming increasingly evident that hypertension in pregnancy may be associated with primarily high cardiac output or high peripheral resistance. A knowledge of the underlying type of hypertension may allow more rational treatment of these conditions in pregnancy rather than therapeutic attempts at controlling blood pressure by any means possible as an end in itself.

The influence of prenatal exercise and pre-eclampsia on maternal vascular function

During healthy pregnancy, the cardiovascular system undergoes diverse adaptations to support adequate transfer of oxygen and nutrients from mother to fetus. In order to accommodate the large expansion of blood volume and associated cardiac output, the structure, mechanics, and function of the arteries are altered. Specifically, in healthy pregnancy there is a remodeling of arteries (increased angiogenesis and vasodilation), a generalized reduction in arterial stiffness (increased compliance), and an enhanced endothelial function. The development of pregnancy complications, specifically pre-eclampsia, is associated with poor placentation (decreased angiogenesis), increased arterial stiffness, and vascular dysfunction (reduced endothelial function). Many of the positive adaptations that occur in healthy pregnancy are enhanced in response to chronic exercise. Specifically, placental angiogenesis and endothelial function have been shown to improve to a greater extent in women who are active during their pregnancy compared with those who are not. Prenatal exercise may be important in helping to reduce the risk of vascular dysfunction in pregnancy. However, our knowledge of the vascular adaptations resulting from maternal exercise is limited. This review highlights maternal vascular adaptations occurring during healthy pregnancy, and contrasts the vascular maladaptation associated with pre-eclampsia. Finally, we discuss the role of prenatal exercise on vascular function in the potential prevention of vascular complications associated with pre-eclampsia.

Effect of Pregnancy on Ventricular and Aortic Dimensions in Repaired Tetralogy of Fallot

Background

The aim was to assess whether cardiovascular adaptation to pregnancy in women with repaired tetralogy of Fallot (TOF) adversely affects hemodynamic stability, in particular with respect to right ventricular (RV) dilatation, pulmonary regurgitation, or aortic root dilatation.

Methods and Results

This was a retrospective cohort study of women with repaired TOF with paired cardiovascular magnetic resonance scans before and after their first pregnancy (baseline RV end systolic volume index 49 mL/m² and RV end diastolic volume index 118 mL/m²) matched with a comparison group of nulliparous women with TOF. Cases were matched for age at baseline cardiovascular magnetic resonance scan, time between follow‐up of cardiovascular magnetic resonance scans, QRS duration, RV ejection fraction, and indexed RV end systolic and diastolic volume at baseline. Effect of pregnancy and time on parameters was assessed using mixed‐effects modelling. Nineteen women with repaired TOF who had completed their first pregnancy were identified and matched with 38 nulliparous women. We observed no deleterious effects of pregnancy on RV volumes, aortic dimensions, or exercise data. There was an effect of pregnancy observed in both left ventricular end diastolic volume and left ventricular stroke volume, consistent with a sustained small increase in left ventricular stroke volume attributed to pregnancy (53–55 mL/m²).

Conclusions

Women with repaired TOF and with mild‐to‐moderate RV dilatation considering pregnancy can be reassured that pregnancy is unlikely to cause deterioration in their cardiovascular status. We recommend that women are routinely assessed and followed up before and after pregnancy and that prepregnancy counseling is tailored to their individual clinical status.

Muscle sympathetic nerve activity and volume-regulating factors in healthy pregnant and nonpregnant women

Healthy, normotensive human pregnancies are associated with striking increases in both plasma volume and vascular sympathetic nerve activity (SNA). In nonpregnant humans, volume-regulatory factors including plasma osmolality, vasopressin, and the renin-angiotensin-aldosterone system have important modulatory effects on control of sympathetic outflow. We hypothesized that pregnancy would be associated with changes in the relationships between SNA (measured as muscle SNA) and volume-regulating factors, including plasma osmolality, plasma renin activity, and arginine vasopressin (AVP). We studied 46 healthy, normotensive young women (23 pregnant and 23 nonpregnant). We measured SNA, arterial pressure, plasma osmolality, plasma renin activity, AVP, and other volume-regulatory factors in resting, semirecumbent posture. Pregnant women had significantly higher resting SNA (38 ± 12 vs. 23 ± 6 bursts/min in nonpregnant women), lower osmolality, and higher plasma renin activity and aldosterone (all P < 0.05). Group mean values for AVP were not different between groups [4.64 ± 2.57 (nonpregnant) vs. 5.17 ± 2.03 (pregnant), P > 0.05]. However, regression analysis detected a significant relationship between individual values for SNA and AVP in pregnant (r = 0.71, P < 0.05) but not nonpregnant women (r = 0.04). No relationships were found for other variables. These data suggest that the link between AVP release and resting SNA becomes stronger in pregnancy, which may contribute importantly to blood pressure regulation in healthy women during pregnancy.NEW & NOTEWORTHY Sympathetic nerve activity and blood volume are both elevated during pregnancy, but blood pressure is usually normal. Here, we identified a relationship between vasopressin and sympathetic nerve activity in pregnant but not nonpregnant women. This may provide mechanistic insights into blood pressure regulation in normal pregnancy and in pregnancy-related hypertension.

Endothelial Dysfunction in Severe Preeclampsia is Mediated by Soluble Factors, Rather than Extracellular Vesicles

In severe early-onset preeclampsia (sPE) the placenta releases soluble angiogenesis-regulating proteins, trophoblast-derived fragments, and extracellular vesicles (EVs). Their relative importance in disease pathogenesis is not presently understood. We explanted placental villi from healthy and sPE women then separated the media into: total-conditioned, EV-depleted and EV-enriched media. Three fractions were compared for; angiogenic protein secretion by ELISA, angiogenic and inflammation gene mRNA expression and leukocyte adhesion assay. sPE placental villi secreted significantly less PlGF (70 ± 18 pg/mL) than preterm controls (338 ± 203; p = 0.03). sFlt-1:PlGF ratios in total-conditioned (115 ± 29) and EV-depleted media (136 ± 40) from sPE placental villi were significantly higher than in EV-enriched media (42 ± 12; p < 0.01) or any preterm or term media. Fluorescent-labeled EVs derived across normal gestation, but not from sPE, actively entered HUVECs. From sPE placental villi, the soluble fraction, but not EV-enriched fraction, significantly repressed angiogenesis (0.83 ± 0.05 fold, p = 0.02), induced HO-1 mRNA (15.3 ± 5.1 fold, p < 0.05) and induced leukocyte adhesion (2.2 ± 0.4 fold, p = 0.04). Soluble media (total-conditioned and EV-depleted media) from sPE placental villi induced endothelial dysfunction in HUVEC, while the corresponding EV-enriched fraction showed no such effects. Our data suggest that soluble factors including angiogenesis-regulating proteins, dominate the vascular pathology of this disease.

Heart Disease and Pregnancy

Cardiac disease remains a major cause of morbidity and mortality in pregnant and post-partum women, although progress has been made, with specialist joint obstetric-cardiology clinics providing an integrated, safe and personalised service to these women. As a result, fewer non-specialist cardiologists are managing women in pregnancy with cardiovascular disease. The aim of this review is to provide a brief overview of current knowledge and practice in the field, with an emphasis on the major physiological changes which occur during pregnancy, focussing on progress through the trimesters, clinical assessment in pregnancy, management of delivery (concentrating on managed vaginal delivery), drug treatment, key conditions and risk assessment. The latter factor is particularly important in terms of being able to identify high-risk women earlier and to counsel them appropriately. Pregnant women with cardiovascular conditions can, with appropriate knowledge and counselling, be managed safely in specialist multidisciplinary services, but there is a need for cardiologists to understand the key changes and risks involved in pregnancy, delivery and the post-partum period.

Impact of Immune Deficiency on Remodeling of Maternal Resistance Vasculature 4 Weeks Postpartum in Mice

Pregnancy manifests changes in the vascular and immune systems that persist postpartum (PP), have important implications for future pregnancies, and may modify responses to cardiovascular stress in late life. The association between immune and vascular function and the generation or progression of cardiovascular disease beg the question of whether altered immunity modifies pregnancy-induced changes in the vasculature. Our objective was to compare changes in the function and remodeling of systemic resistance vessels 4 weeks PP in normal C57BL/6 (B6), and immunodeficient mice recombinase 1-deficient/B6 ( Rag1^-/-). Immune deficiency did not change the responsiveness to acetylcholine (ACh) and phenylephrine at baseline but decreased arterial distensibility and increased stiffness PP. Adoptive transfer of CD8 T cells into Rag1^-/- mice decreased the response to ACh while increasing distensibility and wall thickness. When compared to PP Rag1^-/-, vessels from PP CD4-deficient mice, which have B cells and CD8 T cells, but no CD4 cells, show increased distensibility and decreased responsiveness to ACh in a pattern similar to that seen in Rag1^-/- given CD8 T cells prior to mating. These studies suggest a key role for T cell, particularly CD8 T cell, associated factors in the PP remodeling of maternal resistance vessels.

Bioimpedance cardiography in pregnancy: A longitudinal cohort study on hemodynamic pattern and outcome

Background

Pregnancy associated cardiovascular pathologies have a significant impact on outcome for mother and child. Bioimpedance cardiography may provide additional outcome-relevant information early in pregnancy and may also be used as a predictive instrument for pregnancy-associated diseases.

Methods

We performed a prospective longitudinal cohort trial in an outpatient setting and included 242 pregnant women. Cardiac output and concomitant hemodynamic data were recorded from 11^th–13^th week of gestation every 5^th week as well as at two occasions post partum employing bioimpedance cardiography.

Results

Cardiac output increased during pregnancy and peaked early in the third trimester. A higher heart rate and a decreased systemic vascular resistance were accountable for the observed changes. Women who had a pregnancy-associated disease during a previous pregnancy or developed hypertension or preeclampsia had a significantly increased cardiac output early in pregnancy. Furthermore, an effect of cardiac output on birthweight was found in healthy pregnancies and could be confirmed with multiple linear regression analysis.

Conclusions

Cardiovascular adaptation during pregnancy is characterized by distinct pattern described herein. These may be altered in women at risk for preeclampsia or reduced birthweigth. The assessment of cardiac parameters by bioimpedance cardiography could be performed at low costs without additional risks.