Changes in baroreceptor sensitivity for heart rate during normotensive pregnancy and the puerperium

Blake, Melanie J.; Martin, A; Manktelow, Bradley N; Armstrong, Charles A.; Halligan, Aidan; Panerai, Ronney B.; Potter, John F.

doi:10.1042/cs0980259

Cited by 50 publications

(28 citation statements)

References 33 publications

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“…In support of this hypothesis, decreases in insulin sensitivity (40,47,100,114,141,167) and baroreflex gain (16,24,47,122) exhibit the same time course during gestation in humans, rabbits (Fig. 3), and rats.…”

Section: Insulin Resistance: a Contributor To Pregnancy-induced Decrementioning

confidence: 56%

“…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 resistance. Since then, arterial baroreflex impairment has been documented in several species studied in the conscious state, including dogs (23), rats (24,124), rabbits (21,97,162), goats (152), sheep (104,123), and humans (16,79,122,164,175,193). Reflex responses to atrial stretch are also blunted (51,94,95,103), which may contribute to retention of the expanded blood volume.…”

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confidence: 99%

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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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Section: Insulin Resistance: a Contributor To Pregnancy-induced Decrementioning

confidence: 56%

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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“…In contrast, the sensitivity and the number of reflex events are unchanged in PE compared to healthy pregnant women, although these patients showed the most alterations in BPV. However, it should be at least mentioned that healthy normotensive pregnancies are characterized by a significant reduction of baroreflex events 10,22 that could be explained by an increase in baroreflex threshold. Thus, it cannot be distinguished whether the discovered increase in baroreflex events in PIH is caused exclusively by an increased BPV or at least partly by a threshold shift.…”

Section: Discussionmentioning

confidence: 99%

Baroreflex sensitivity, heart rate, and blood pressure variability in hypertensive pregnancy disorders

et al. 2004

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Hypertensive pregnancy disorders are a leading cause of perinatal and maternal morbidity and mortality. Heart rate variability (HRV), blood pressure variability (BPV), and baroreflex sensitivity (BRS) are relevant predictors of cardiovascular risk in humans. The aim of the study was to evaluate whether HRV, BPV, and BRS differ between distinct hypertensive pregnancy disorders. Continuous heart rate and blood pressure recordings were performed in 80 healthy pregnant women as controls (CON), 19 with chronic hypertension (CH), 18 with pregnancy-induced hypertension (PIH), and 44 with pre-eclampsia (PE). The data were assessed by time and frequency domain analysis, nonlinear dynamics, and BRS. BPV is markedly altered in all three groups with hypertensive disorders compared to healthy pregnancies, whereby changes were most pronounced in PE patients. Interestingly, this increase in PE patients did not lead to elevated spontaneous baroreflex events, while BPV changes in both the other hypertensive groups were paralleled by alterations in baroreflex parameters. The HRV is unaltered in CH and PE but significantly impaired in PIH. We conclude that parameters of the HRV, BPV, and BRS differ between various hypertensive pregnancy disorders. Thus, distinct clinical manifestations of hypertension in pregnancy have different pathophysiological, regulatory, and compensatory mechanisms.

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“…As discussed above, the sympathetic hyperactivity was not related to reflex control, race, or constitutional factors, and it could be the mechanism by which the arterial blood pressure and vascular resistance tend to normalize during the third trimester of normal pregnancy. 6,7,19,25 The excessive increase in sympathetic output found in patients with PIH may by implication be involved in the development of their hypertension. From the published evidence, although limited, it is possible to speculate that the increase in central sympathetic activity in pregnancy is related to hormonal changes, of which there are many.…”

Section: Discussionmentioning

confidence: 99%

“…During the third trimester of normal pregnancy, arterial blood pressure tends to rise toward normal nonpregnant levels, 6,7 but it is unknown whether central sympathetic drive is involved in this process. The use of indirect measures of sympathetic output, such as changes in hemodynamic variables and circulating catecholamines, has yielded conflicting results in both normal and hypertensive pregnancy.…”

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confidence: 99%

Sympathetic Neural Mechanisms in Normal and Hypertensive Pregnancy in Humans

et al. 2001

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Background-Direct recordings from peripheral sympathetic nerves have shown an increased sympathetic drive in pregnancy-induced hypertension (PIH) and preeclampsia (PE). It is unknown whether sympathetic drive is altered in normal pregnancy, when arterial blood pressure can be normal or relatively low. The aim of this study was to measure and compare peripheral sympathetic discharge, its vasoconstrictor effect and its baroreceptor control, during pregnancy and postpartum in women with normal pregnancy (NP) and PIH and in normotensive nonpregnant (NN) women. Methods and Results-Twenty-one women with NP, 18 women with PIH, and 21 NN women had muscle sympathetic nerve activity assessed from multiunit discharges (MSNA) and from single units with defined vasoconstrictor properties (s-MSNA). The s-MSNA in NP (38Ϯ6.6 impulses/100 beats) was greater (PϽ0.05) than in NN women (19Ϯ1.8 impulses/100 beats) despite similar age and body weight but less than in PIH women (PϽ0.001) (146Ϯ23.5 impulses/100 beats). MSNA followed a similar trend. Cardiac baroreceptor reflex sensitivity (BRS) was impaired in NP and PIH women relative to NN. After delivery, sympathetic activity decreased to values similar to those obtained in NN, and there was an increase in BRS. In women with NP, the decrease in sympathetic output occurred despite an insignificant change in blood pressure. Conclusions-Central sympathetic output was increased in women with normal pregnancy and was even greater in the hypertensive pregnant group. The findings suggest that the moderate sympathetic hyperactivity during the latter months of normal pregnancy may help to return the arterial pressure to nonpregnant levels, although when the increase in activity is excessive, hypertension may ensue. (Circulation. 2001;104:2200-2204.)

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Changes in baroreceptor sensitivity for heart rate during normotensive pregnancy and the puerperium

Cited by 50 publications

References 33 publications

Pregnancy and the endocrine regulation of the baroreceptor reflex

Pregnancy and the endocrine regulation of the baroreceptor reflex

Baroreflex sensitivity, heart rate, and blood pressure variability in hypertensive pregnancy disorders

Sympathetic Neural Mechanisms in Normal and Hypertensive Pregnancy in Humans

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