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

Abstract

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 .

Maternal posture-physiology interactions in human pregnancy: a narrative review

“…As gestation advances, however, the ANS shifts toward a higher sympathetic and lower parasympathetic tone ( Blake et al, 1979 ; Ekholm et al, 1993 ; Kuo et al, 2000 ; Corrêa et al, 2019 ), especially in supine posture, ( DSilva et al, 2014 ; Kuo et al, 2000 ; Blake et al, 1979 ). This biphasic change in ANS activity in pregnancy may be a result of the competing influences and resultant hemodynamic effects of physiologic volume expansion in the second trimester versus aortocaval compression from the enlarging gravid uterus in the third trimester ( DSilva et al, 2014 ; Kuo et al, 2000 ; Maser et al, 2014 ).…”

Increased respiratory modulation of cardiovascular control reflects improved blood pressure regulation in pregnancy

“…Spradley et al ( Spradley, 2019 ) showed that baroreflex sensitivity in healthy pregnant women was not altered, while Garg et al ( Garg et al, 2020 ) reported a decrease in cardiovagal modulation and baroreflex sensitivity towards the end of a healthy pregnancy. Corrêa et al ( Da Silva Corrêa et al, 2019 ) found a decrease in parasympathetic modulation and baroreflex sensitivity of healthy pregnancy at rest but a preserved baroreflex response during posture changes. Usselman et al ( Usselman et al, 2015b ) found maintenance of cardiovagal baroreflex but decreased sympathetic baroreflex gain, indicating that the baroreflex might not be the main mechanism of MSNA modulation.…”

Neuromuscular disorders in pregnancy

“…Pregnancy affects autonomic responses in multiple ways. Various studies have documented various differences, which are further altered by preeclampsia ( Chaswal et al, 2018 ; da Corrêa et al, 2019 ; Garg et al, 2020 ). Autonomic neuropathy is uncommon but can occur in young women.…”