The Effects of Postural Changes of Baroreflex Gain in Normal and Hypertensive Pregnancies

Miyake, Yoichi; Ohnishi, Masato; Fujii, Torao; Yamamoto, Tatsuo; Yoneda, Chika; S, Takahashi; Ichimaru, Yuhei

doi:10.1081/ceh-100108712

Cited by 7 publications

(16 citation statements)

References 12 publications

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“…The higher HR and lower HP mean are compatible with these changes. These results are in agreement with several studies that reported a lower parasympathetic contribution in pregnancy [11,15,35]. Expansion of blood volume may cause stretching of the sinoatrial node leading to a less effective vagal modulation.…”

Section: Discussionsupporting

confidence: 93%

“…Some works advocated the activation of the renin-angiotensin system to explain the increase of sympathetic activity observed during pregnancy [38]. Some studies confirmed at the cardiac level the sympathetic activation observed at the level of muscle nerve sympathetic activity [37] with the observation the ratio of LF to HF power increased during pregnancy [14,15]. Our study LFnu did not show differences between groups, thus pointing to a preservation of the cardiac sympathetic control during pregnancy.…”

Section: Discussionsupporting

confidence: 78%

“…However, the exact mechanisms underlying the changes in autonomic cardiovascular modulation in pregnancy is not well established, especially those at the basis of the modifications of the cardiac and vascular controls. This led to controversial findings about the presumed sympathetic activation during pregnancy [14,15], as well as the preservation of the sympatho-vagal balance [13]. Also the timing at which the presumed modifications of the cardiovascular regulation occur is also controversial [1,12].…”

Section: Introductionmentioning

confidence: 99%

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Cardiovascular autonomic modulation and baroreflex control in the second trimester of pregnancy: A cross sectional study

et al. 2019

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Purpose The aim is to evaluate and characterize cardiovascular autonomic control and baroreflex function and their response to an orthostatic stressor in the second trimester of pregnancy via time, frequency, information and symbolic analyses. Methods We evaluated 22 women at 18 weeks of pregnancy, labeled as pregnant group (PG) (30.8±4.4 years), and 22 non-pregnant women (29.8±5.4 years), labeled as control group (CG). Electrocardiogram, non-invasive photoplethysmographic arterial pressure (AP) and respiratory signals were recorded at rest at left lateral decubitus (REST) and during active standing (STAND) for 10 minutes. The heart period (HP) variability and systolic AP (SAP) variability were assessed in the frequency domain. High frequency (HF) and low frequency (LF) spectral indexes were computed. Nonlinear indexes such as symbolic markers (0V%, 1V%, 2LV% and 2UV% indexes), Shannon entropy (SE) and normalized complexity index (NCI) were calculated as well. Baroreflex control was assessed by cross-spectral HP-SAP analysis. We computed baroreflex sensitivity (BRS), HP-SAP squared coherence (K 2 ) and phase in LF and HF bands. Results At REST, the PG had lower mean, variance and HF power of HP series and lower K 2 (LF), BRS(LF) and BRS(HF) than the CG. During STAND, CG and PG decreased the mean, CI, NCI and 2UV% and increased 0V% of the HP series and augmented the SAP variance. LFabs of SAP series increased during STAND solely in CG. BRS(HF) was reduced during in both PG and CG, while HFabs of HP series did not diminish during STAND either in PG or CG. Complexity of the autonomic control was similar in PG and CG regardless of the experimental condition. Conclusion We conclude that the second trimester of pregnancy was characterized by a lower parasympathetic modulation and reduced BRS at REST, preserved complexity of cardiac and vascular controls, limited sympathetic response to STAND and general conservation of the baroreflex responses to posture changes. Trial registration Begistro Brasileiro de Ensaios clínicos, Number: RBR-9s8t88 .

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Section: Discussionsupporting

confidence: 93%

Section: Discussionsupporting

confidence: 78%

Section: Introductionmentioning

confidence: 99%

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Cardiovascular autonomic modulation and baroreflex control in the second trimester of pregnancy: A cross sectional study

et al. 2019

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“…The primary role of the arterial baroreflex is the immediate and short-term adjustment of BP following perturbations around an existing mean pressure [ 32 ]. Baroreflex sensitivity (BRS) was reported to decrease from term to the postpartum period in normotensive pregnancy [ 32 – 35 ]. Valdes et al [ 36 ] demonstrated a progressive blunting of the heart rate response to tilt as pregnancy progressed, suggesting a decrease in BRS in late pregnancy.…”

Section: Discussionmentioning

confidence: 99%

Maternal cardiovascular and endothelial function from first trimester to postpartum

et al. 2018

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ObjectiveTo explore noninvasively the complex interactions of the maternal hemodynamic system throughout pregnancy and the resulting after-effect six weeks postpartum.MethodsEighteen women were tested beginning at the 12th week of gestation at six time-points throughout pregnancy and six weeks postpartum. Heart rate, heart rate variability, blood pressure, pulse transit time (PTT), respiration, and baroreceptor sensitivity were analyzed in resting conditions. Additionally, hemoglobin, asymmetric and symmetric dimethylarginine and Endothelin (ET-1) were obtained.ResultsHeart rate and sympathovagal balance favoring sympathetic drive increased, the vagal tone and the baroreflex sensitivity decreased during pregnancy. Relative sympathetic drive (sympathovagal balance) reached a maximum at 6 weeks postpartum whereas the other variables did not differ compared to first trimester levels. Postpartum diastolic blood pressure was higher compared to first and second trimester. Pulse transit time and endothelial markers showed no difference throughout gestation. However, opposing variables PTT and asymmetric dimethylarginine (ADMA) were both higher six weeks postpartum.ConclusionsThe sympathetic up regulation throughout pregnancy goes hand in hand with a decreased baroreflex sensitivity. In the postpartum period, the autonomic nervous system, biochemical endothelial reactions and PTT show significant and opposing changes compared to pregnancy findings, indicating the complex aftermath of the increase of blood volume, the changes in perfusion strategies and blood pressure regulation that occur in pregnancy.

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“…Pregnant women are prone to orthostatic hypotension, due to blunted reflex activation of the sympathetic nervous system and inadequate peripheral vasoconstriction (56,122,132). Moreover, in many species, pregnancy interferes with the normal ability to maintain arterial pressure during hemorrhage (26,36,99,152,186).…”

mentioning

confidence: 99%

Pregnancy and the endocrine regulation of the baroreceptor reflex

Brooks

Dampney

Heesch

2010

American Journal of Physiology-Regulatory, Integrative and Comp

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-The purpose of this review is to delineate the general features of endocrine regulation of the baroreceptor reflex, as well as specific contributions during pregnancy. In contrast to the programmed changes in baroreflex function that occur in situations initiated by central command (e.g., exercise or stress), the complex endocrine milieu often associated with physiological and pathophysiological states can influence the central baroreflex neuronal circuitry via multiple sites and mechanisms, thereby producing varied changes in baroreflex function. During pregnancy, baroreflex gain is markedly attenuated, and at least two hormonal mechanisms contribute, each at different brain sites: increased levels of the neurosteroid 3␣-hydroxydihydroprogesterone (3␣-OH-DHP), acting in the rostral ventrolateral medulla (RVLM), and reduced actions of insulin in the forebrain. 3␣-OH-DHP appears to potentiate baroreflex-independent GABAergic inhibition of premotor neurons in the RVLM, which decreases the range of sympathetic nerve activity that can be elicited by changes in arterial pressure. In contrast, reductions in the levels or actions of insulin in the brain blunt baroreflex efferent responses to increments or decrements in arterial pressure. Although plasma levels of angiotensin II are increased in pregnancy, this is not responsible for the reduction in baroreflex gain, although it may contribute to the increased level of sympathetic nerve activity in this condition. How these different hormonal effects are integrated within the brain, as well as possible interactions with additional potential neuromodulators that influence baroreflex function during pregnancy and other physiological and pathophysiological states, remains to be clearly delineated.3␣-hydroxy-dihydroprogesterone; angiotensin II; insulin; paraventricular nucleus of the hypothalamus NORMAL PREGNANCY is characterized by profound changes in fluid and electrolyte balance and blood pressure regulation. Blood volume and cardiac output increase by 30 -50%, but arterial pressure falls due to even greater decreases in systemic vascular resistance (120,138,189). These hemodynamic alterations are evident early in pregnancy, precede the increases in uterine blood flow, and are sustained until parturition (127,138,189). Considerable data implicate increases in relaxin and nitric oxide (NO) in the systemic vasodilation induced by pregnancy (20,127,128,177,196). In addition, peripheral vascular sensitivity to circulating vasoconstrictors including vasopressin, angiotensin II (ANG II), and norepinephrine (NE) is decreased (50,71,154).Unlike the hemodynamic changes, which likely subserve adequate fetal development, an adverse consequence of normal pregnancy is a marked impairment of the arterial baroreceptor reflex. This change was first noted by Humphreys and Joels (97,98) in an extensive series of studies in anesthetized pregnant rabbits, in which reductions in carotid sinus pressure failed to elicit normal increases in arterial pressure and peripheral vascular resistanc...

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The Effects of Postural Changes of Baroreflex Gain in Normal and Hypertensive Pregnancies

Cited by 7 publications

References 12 publications

Cardiovascular autonomic modulation and baroreflex control in the second trimester of pregnancy: A cross sectional study

Cardiovascular autonomic modulation and baroreflex control in the second trimester of pregnancy: A cross sectional study

Maternal cardiovascular and endothelial function from first trimester to postpartum

Pregnancy and the endocrine regulation of the baroreceptor reflex

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