Association of sympathovagal imbalance with cardiovascular risks in young prehypertensives

Potential consequences of cardioneuroablation for vasovagal syncope: A call for appropriately designed, sham-controlled clinical trials

Cardioneuroablation (CNA) is being increasingly used to treat patients with vasovagal syncope (VVS). Bradycardia, in the cardioinhibitory subtype of VVS, results from transient parasympathetic overactivity leading to sinus bradycardia and/or atrioventricular block. By mitigating parasympathetic overactivity, CNA has been shown to improve VVS symptoms in clinical studies with relatively small sample sizes and short follow-up periods (<5 years) at selected centers. However, CNA may potentially tip the autonomic balance to a state of sympathovagal imbalance with attenuation of cardiac parasympathetic activity. A higher heart rate is associated with adverse cardiovascular events and increased mortality in healthy populations without cardiovascular diseases. Chronic sympathovagal imbalance may also affect the pathophysiology of spectra of cardiovascular disorders including atrial and ventricular arrhythmias. This review addresses potential long-term pathophysiological consequences of CNA for VVS.

Differences in heart rate responses to upright posture are associated with variations in the high-frequency power of heart rate variability

High resting heart rate is a cardiovascular risk factor, but limited data exist on the underlying hemodynamics and reproducibility of supine-to-upright increase in heart rate. We recorded noninvasive hemodynamics in 574 volunteers [age, 44.9 yr; body mass index (BMI), 26.4 kg/m2; 49% male] during passive head-up tilt (HUT) using whole body impedance cardiography and radial artery tonometry. Heart rate regulation was evaluated using heart rate variability (HRV) analyses. Comparisons were made between quartiles of supine-to-upright heart rate changes, in which heart rate at rest ranged 62.6-64.8 beats/min (P = 0.285). The average upright increases in heart rate in the quartiles 1-4 were 4.7, 9.9, 13.5, and 21.0 beats/min, respectively (P < 0.0001). No differences were observed in the low-frequency power of HRV, whether in the supine or upright position, or in the high-frequency power of HRV in the supine position. Upright high-frequency power of HRV was highest in quartile 1 with lowest upright heart rate and lowest in quartile 4 with highest upright heart rate. Mean systolic blood pressure before and during HUT (126 vs. 108 mmHg) and the increase in systemic vascular resistance during HUT (650 vs. 173 dyn·s/cm5/m2) were highest in quartile 1 and lowest in quartile 4. The increases in heart rate during HUT on three separate occasions several weeks apart were highly reproducible (r = 0.682) among 215 participants. To conclude, supine-to-upright increase in heart rate is a reproducible phenotype with underlying differences in the modulation of cardiac parasympathetic tone and systemic vascular resistance. As heart rate at rest influences prognosis, future research should elucidate the prognostic significance of these phenotypic differences.NEW & NOTEWORTHY Subjects with similar supine heart rates are characterized by variable increases in heart rate during upright posture. Individual heart rate increases in response to upright posture are highly reproducible as hemodynamic phenotypes and present underlying differences in the modulation of cardiac parasympathetic tone and systemic vascular resistance. These results indicate that resting heart rate obtained in the supine position alone is not an optimal means of classifying people into groups with differences in cardiovascular function.

Arterial Baroreflex Dysfunction Promotes Neuroinflammation by Activating the Platelet CD40L/Nuclear Factor Kappa B Signaling Pathway in Microglia and Astrocytes

Arterial baroreflex (ABR) dysfunction has previously been associated with neuroinflammation, the most common pathological feature of neurological disorders. However, the mechanisms mediating ABR dysfunction-induced neuroinflammation are not fully understood. In the present study, we investigated the role of platelet CD40 ligand (CD40L) in neuroinflammation in an in vivo model of ABR dysfunction, and microglia and astrocyte activation in vitro. ABR dysfunction was induced in Sprague‒Dawley rats by sinoaortic denervation (SAD). We used ELSA and immunofluorescence to assess the effect of platelet CD40L on glial cell polarization and the secretion of inflammatory factors. By flow cytometry, we found that rats subjected to SAD showed a high level of platelet microaggregation and upregulation of CD40L on the platelet surface. The promotion of platelet invasion and accumulation was also observed in the brain tissues of rats subjected to SAD. In the animal model and cultured N9 microglia/C6 astrocytoma cells, platelet CD40L overexpression promoted neuroinflammation and activated M1 microglia, A1 astrocytes, and the nuclear factor kappa B (NFκB) signaling pathway. These effects were partially blocked by inhibiting platelet activity with clopidogrel or inhibiting CD40L-mediated signaling. Our results suggest that during ABR dysfunction, CD40L signaling in platelets converts microglia to the M1 phenotype and astrocytes to the A1 phenotype, activating NFκB and resulting in neuroinflammation. Thus, our study provides a novel understanding of the pathogenesis of ABR dysfunction-induced neuroinflammation and indicates that targeting platelet CD40L is beneficial for treating central nervous system (CNS) disorders associated with ABR dysfunction.

Hypertension attenuates the link of osteoprotegerin to reduced baroreflex sensitivity in type 2 diabetes mellitus patients on oral antidiabetic and antihypertensive therapy - a cross sectional study

PURPOSE

Decreased baroreflex sensitivity (BRS) has been shown to be a marker of cardiovascular (CV) risk. In the present study, the difference in CV risk biomarkers in type 2 diabetes (T2D) patients receiving oral antidiabetic drugs (OAD) with and without hypertension has been assessed.

MATERIALS AND METHODS

Ninety-two T2D patients on OAD without hypertension (control group) and eighty-eight diabetic patients with hypertension on OAD and antihypertensive drugs (test group) matched for age, gender, body mass index, serum glucose, glycated haemoglobin, and duration of the disease were recruited for the study. Their blood pressure (BP) variability including BRS, heart rate variability (HRV), insulin, lipid profile, osteoprotegerin (OPG), and tumor necrosis factor-α (TNF-α) were estimated. The association of various factors with BRS was assessed by Spearman correlation and multiple regression analysis.

RESULTS

BRS was decreased (13.90 ± 5.27 vs 6.76 ± 4.58), HRV sympathetic indices [LFnu, LF-HF ratio (1.30 ± 0.49 vs 1.93 ± 0.62)], HOMA-IR, atherogenic index of plasma (AIP), OPG (223.08 ± 103.86 vs 287.60 ± 121.36) and TNF-α were increased, and parasympathetic indices [TP (1012.90 ± 316.18 vs 625.88 ± 229.84), RMSSD, SDNN, NN50, pNN50] were decreased in the test group compared to control group. In control group, parasympathetic indices, AIP, OPG, and TNF-α had a significant correlation and OPG had an independent association (β - 0.344; p 0.004) with BRS. In test group, BP, LF-HF ratio, parasympathetic indices, AIP, OPG, and TNF-α had significant correlation, and TNF-α alone (β - 0.297; p 0.022) had an independent contribution to decreased BRS.

CONCLUSION

Despite antidiabetic and antihypertensive treatments, T2D patients with hypertension had more cardiometabolic risks in comparison to normotensive T2D patients. Inflammation could be the inciting factor for rise in BP and decrease in BRS (CV risk) in hypertensive T2D patients. Hypertension in diabetes could attenuate the link of OPG to the reduction in BRS. Reduction in BRS could be a physiological marker of CV risk in T2D patients treated with OAD.

Interplay between baroreflex sensitivity, obesity and related cardiometabolic risk factors (Review)

The baroreflex represents a rapid negative feedback system implicated in blood pressure regulation, which aims to prevent blood pressure variations by regulating peripheral vascular tone and cardiac output. The aim of the present review was to highlight the association between baroreflex sensitivity (BRS) and obesity, including factors associated with obesity, such as metabolic syndrome, hypertension, cardiovascular disease and diabetes. For the present review, a literature search was conducted using the PubMed database until August 21, 2021. The searched terms included ‘baroreflex’, and other terms such as ‘sensitivity’, ‘obesity’, ‘metabolic syndrome’, ‘hypertension’, ‘diabetes’, ‘gender’, ‘aging’, ‘children’, ‘adolescents’, ‘physical activity’, ‘bariatric surgery’, ‘autonomous nervous system’ and ‘cardiometabolic risk factors’. Obesity and its related metabolic disorders can influence baroreflex functionality and decrease BRS, mostly by potentiating sympathetic nervous system activity. Obesity induces inflammation, which can increase sympathetic system activity and lead to a higher incidence of cardiovascular events. Obesity also represents an important risk factor for hypertension through numerous mechanisms; in this setting, dysfunctional baroreceptors are not able to protect against constantly elevated blood pressure. Furthermore, diabetes mellitus and oxidative stress result in deterioration of BRS, whereas aging is also generally related to reduced cardiovagal BRS. Differences in BRS have also been observed between men and women, and overall cardiovagal BRS in healthy women is less intense compared with that in men. BRS appears lower in children with obesity compared with that in children of a healthy weight. Notably, physical exercise can increase BRS in both hypertensive and normotensive subjects, and BRS can also be significantly improved following bariatric surgery and weight loss. In conclusion, obesity and its related metabolic disorders may influence baroreflex functionality and decrease BRS, and baroreceptors cannot protect against the constantly elevated blood pressure in obesity. However, following bariatric surgery and weight loss, BRS can be significantly improved. The present review summarizes the role of obesity and related metabolic risk factors in BRS, providing details on possible mechanisms and shedding light on their interplay leading to autonomic neuropathy.

Cardiac Autonomic Modulation is a Key Factor for High Blood Pressure in Adolescentes

Fundamento

O interesse pela hipertensão em crianças e adolescentes aumentou desde a atualização do sistema de classificação da pressão arterial para comparar com o sistema de classificação dos adultos, alterando a terminologia de “normal alta” para “pré-hipertensão”.

Objetivo

O objetivo deste estudo foi analisar a associação da modulação autonômica cardíaca com os níveis pressóricos dos adolescentes.

Métodos

203 adolescentes foram agrupados de acordo com a pressão arterial sistólica (PAS) e a pressão arterial diastólica (PAD). Um grupo foi caracterizado como pré-hipertensão, e o outro como normotenso. Foram coletadas características antropométricas, cardiovasculares e de qualidade do sono. Inicialmente, os dados foram submetidos ao teste de normalidade Kolmogorov-Smirnov . As variáveis quantitativas contínuas foram analisadas por meio do teste T de Student não pareado. Para análise das variáveis categóricas, foi utilizado o teste qui-quadrado. Um modelo de regressão logística foi realizado. O nível de significância estabelecido foi p<0,05. Os dados foram expressos como média ± desvio padrão e intervalo de confiança. O software R foi utilizado para análise dos dados. O tamanho do efeito foi calculado com a fórmula de Cohen.

Resultados

O grupo pré-hipertensão apresentou aumento da entropia de Shannon e diminuição da variância total. Além disso, no modelo de regressão logística, os adolescentes deste grupo tiveram 1,03 mais chances de ter a entropia de Shannon afetada quando a PAS foi ajustada ao gênero, maturação sexual, tempo escolar, idade, circunferência da cintura e qualidade do sono.

Conclusão

Nossos dados mostram que a modulação autonômica pode desempenhar um papel importante no desenvolvimento da pressão arterial elevada em adolescentes ao controlar fatores como tempo escolar e qualidade do sono.

Effects of 12 Weeks Practice of Yoga on Heart Rate Variability in Males with Type 2 Diabetes Receiving Oral Antidiabetic Drugs: A Randomized Control Trial

Objective: To investigate the effects of 12 weeks practice of a structured yoga module on heart rate variability (HRV) and cardiometabolic risks in patients with type 2 diabetes (T2D) receiving similar kind of oral antidiabetic drugs (OAD) with yoga therapy and without yoga therapy, matched for all the known confounders. Design: Parallel design interventional (randomized control trial) study. Subjects: Eighty treatment-naive males with T2D were randomized into control group (n = 40) and study group (n = 40). Intervention: Study group participants received a structured yoga therapy that included asana and pranayama practice for 12 weeks in addition to OAD, whereas control group participants received OAD alone. Outcome measures: Before and after intervention, BP parameters, rate pressure product (RPP) as the marker of myocardial stress, total power (TP) of HRV, low-frequency to high-frequency (LF-HF) ratio of HRV, homeostatic model of insulin resistance (HOMA-IR), lipid profile and lipid risk factors, malondialdehyde (MDA), and high-sensitive C-reactive protein (hsCRP) were measured. TP of HRV was defined as the primary outcome. Association of TP (the marker of HRV) and LF-HF ratio (the marker of sympathovagal balance) with cardiometabolic parameters was assessed by correlation and regression analyses. Results: After 12 weeks yoga therapy, there was significant reduction in cardiometabolic risks (TP of HRV, RPP, lipid risks factors, levels of MDA, and hsCRP) in study group subjects compared with control subjects that did not receive yoga therapy. All cardiometabolic risk factors were significantly correlated with TP in study group, having maximum significance with homeostatic model of insulin secretion (r = 0.502, p ≤ 0.001). Multiple regression analysis demonstrated the independent contribution of decrease in RPP, HOMA-IR, hsCRP, and MDA to increased TP and decreased LF-HF ratio in T2D patients after yoga therapy. Conclusion: From the results of this study, the authors conclude that 12 weeks practice of a structured yoga module improves TP of HRV, sympathovagal balance, and metabolic functions, and reduce cardiovascular (CV) risks in patients with diabetes who received routine antidiabetic medicines along with yoga therapy, compared with the patients with diabetes who received antidiabetic medicines alone. The reduction in cardiometabolic risks in these patients is linked to the improvement in TP of HRV. Future studies should also include a control group with rapid walking or a similar exercise program of equal time to the yoga intervention group to discern whether it is in fact yoga that is leading to these results and not simply increased CV activity. Clinical Trial Registry of India (No. CTRI/2021/06/034074).

Respiratory Sinus Arrhythmia in Children-Predictable or Random?

Background: Respiratory sinus arrhythmia (RSA) is associated with better health in children.

Aim: The study was conducted to analyze the trajectory of RSA in 10-year-olds.

Methods: A follow-up study on 120 healthy children (62 boys) aged 10.7 ± 0.5 years consisted of a standard 12-lead electrocardiogram, measurements of height, weight and blood pressure. The protocol was repeated after 3 years. Assessment of RSA based on semi-automatic measurements of RR intervals included: the difference between the longest and shortest RR interval duration (pvRSA), the root mean square of differences between successive RR intervals (RMSSD), the standard deviation of the RR interval length (SDNN) and their equivalents corrected for heart rate (RMSSDc and SDNNc).

Results: A the first visit 61.7% of children presented with RSA; 51.7% 3 years later. 23.3% of them had RSA only on the first examination; 13.3% only on the second one. The pvRSA, RMSSD, and SDNN measured in 2019 did not differ significantly from their 2016 equivalents (p > 0.05). The decline in RSA defined by RMSSD was noted in 52.5% of children and in 54.2% when defined by SDNN. The corrected values decreased in 68.3 and 64.2% of the participants for RMSSDc and SDNNc, respectively. The students with RSA at both visits had lower heart rate (p < 0.001) and systolic blood pressure (p = 0.010) compared to those with rhythmic electrocardiograms.

Conclusions: RSA in children is changeable, though its measurable indices should be adjusted to heart rate.

Increased Incidence of Premenstrual Syndrome in Females with Palmar Hyperhidrosis

Background: Premenstrual syndrome (PMS) is a common disorder affecting the quality of life of women of reproductive age. In a previous study, sex hormone imbalances and alterations in autonomic function were present in PMS, with parasympathetic dysfunction and sympathetic overactivity during the late luteal phase. Palmar hyperhidrosis (PH) presents with oversweating, heat and emotional stimulation, sympathetic hyperactivity and parasympathetic hypofunction. We hypothesized that the incidence of PMS is increased in females with PH. Methods: Data were retrieved from the Taiwanese National Health Insurance Database. The patients with PH were identified by the International Classification of Disease, 9th Revision, Clinical Modification (ICD-9-CM) disease code 780.8. Female patients matched by age and index day were used as the control group. The incidence of PMS was considered an outcome by the ICD-9-CM disease code 625.4. The factors related to PMS were analyzed by Cox regression. Results: The adjusted hazard ratio for the incidence of PMS was 1.276 (95% confidence interval: 1.05–1.488) in females with PH. Conclusions: This study found a positive correlation between PMS and female PH patients. Patients and physicians must understand the relationship of PMS with autonomic function alterations and other risk factors to prevent this problematic disorder.

Obesity does not Impair Ambulatory Cardiovascular and Autonomic Responses Post-exercise

This study aimed to assess whether obesity and/or maximal exercise can change 24 h cardiac autonomic modulation and blood pressure in young men. Thirty-nine men (n: 20; 21.9±1.8 kg·m^-2, and n: 19; 32.9±2.4 kg·m^-2) were randomly assigned to perform a control (non-exercise) and an experimental day exercise (after maximal incremental test). Cardiac autonomic modulation was evaluated through frequency domain heart rate variability (HRV). Obesity did not impair the ambulatory HRV (p>0.05), however higher diastolic blood pressure during asleep time (p=0.02; group main effect) was observed. The 24 h and awake heart rate was higher on the experimental day (p<0.05; day main effect), regardless of obesity. Hypotension on the experimental day, compared to control day, was observed (p<0.05). Obesity indicators were significantly correlated with heart rate during asleep time (Rho=0.34 to 0.36) and with ambulatory blood pressure(r/Rho=0.32 to 0.53). Furthermore, the HRV threshold workload was significantly correlated with ambulatory heart rate (r/Rho=- 0.38 to-0.52). Finally, ambulatory HRV in obese young men was preserved; however, diastolic blood pressure was increased during asleep time. Maximal exercise caused heart rate increase and 24h hypotension, with decreased cardiac autonomic modulation in the first hour, regardless of obesity.

Decreased baroreflex sensitivity is associated with cardiometabolic risks and prehypertension status in early-postmenopausal women

OBJECTIVE

We studied the link of decreased baroreflex sensitivity (BRS) to cardiometabolic risks and prehypertension status in postmenopausal women during their early menopausal phase.

METHODS

Premenopausal women (n = 55) and early-postmenopausal women (n = 50) of age group between 40 and 55 years were recruited for the study, and their anthropometric parameters, complete battery of autonomic function tests (AFT), BRS, hormone levels, and cardiometabolic risk parameters were measured and compared between two groups. Correlation analysis of BRS with various physiological and biochemical parameters in these two groups were performed. Multiple regression analysis of BRS with various other associated factors in postmenopausal subjects and bivariate logistic regression analysis for assessing prediction of prehypertension status by BRS in postmenopausal group were performed.

RESULTS

There was a significant difference in AFT and metabolic parameters between premenopausal and postmenopausal women. Sympathovagal imbalance (increased sympathetic and decreased parasympathetic) was prominent in early-postmenopausal women. Decreased BRS, the marker of cardiovascular (CV) risk was found to be significant (P < .001) and correlated with various cardiometabolic parameters in early-postmenopausal subjects. Multiple regression analysis demonstrated that decreased BRS is independently linked to parameters of decreased vagal activity, inflammation, and oxidative stress in early-postmenopausal group. Decreased BRS could predict prehypertension status in early-postmenopausal subjects as confirmed by bivariate logistic regression analysis.

CONCLUSION

Sympathovagal imbalance, decreased BRS and considerable metabolic derangements were observed in women in their early phase of menopause. Decreased BRS appears to be associated with the cardiometabolic risks in these women. Prehypertension status in early-postmenopausal subjects could be predicted by decreased BRS.

Increased osteoprotegerin level is associated with impaired cardiovagal modulation in type-2 diabetic patients treated with oral antidiabetic drugs

Background

An increased osteoprotegerin (OPG) level has been reported in both type-2 diabetes mellitus (T2DM) and cardiovascular diease (CVD) that are linked to sympathovagal imbalance (SVI). We explored the link of osteoprotegerin with cardiovagal modulation in T2DM.

Methods

We assessed fasting serum OPG, high-sensitive C-reactive protein (hsCRP), glucose, insulin and lipid profile in patients having T2DM receiving oral antidiabetic drugs (OAD) (n = 42) compared with age, gender and body composition-matched healthy participants without diabetes (n = 42). Rate pressure product (RPP), spectral indices of heart rate variability (HRV) and body composition were recorded in both the groups. Association of HOMA-IR and OPG with various parameters were assessed.

Results

Osteoprotegerin, HOMA-IR, hsCRP, coronary lipid risk factor were significantly increased, markers of cardiovagal modulation (TP, SDNN, RMSSD) were considerably decreased, ratio of low-frequency to high-frequency (LH-HF ratio), the indicator of SVI, and RPP, the marker of myocardial work stress were significantly higher in patients with diabetes, suggesting an overall elevated CVD risks in them. HOMA-IR was correlated with RMSSD, lipid risk factors and OPG. Rise in OPG was correlated with decreased cardiovagal modulation in patients with diabetes. There was significant contribution of OPG in decreasing TP, suggesting impaired cardiovagal modulation.

Conclusion

T2DM patients receiving OAD had higher cardiometabolic risks compared to age, gender and body composition-matched healthy individuals. Increased level of OPG is linked to decreased cardiovagal modulation in T2DM patients.

Reliability of ultra-short indices for autonomic dysfunction in dyslipidemia

Dyslipidemia is associated with autonomic nervous system (ANS) dysfunction. Heart rate variability (HRV) is a powerful tool for evaluating the ANS and for cardiovascular risk stratification. Yet, the methodologies used are impractical in most clinical settings and therefore, are usually not applied. The current study aimed to evaluate the reliability of ultra-short HRV parameters, which are easily calculated from any standard ECG, as a practical method for ANS study, with a focus on patients with dyslipidemia. Fifty-nine volunteers with dyslipidemia underwent HRV study of parametric and power spectral indices according to accepted methods. Correlations were calculated between ultra-short HRV indices (five 1-min and five 10-s segments) and standard 5-min recordings. Correlations were found between 10-s and 1-min RMSSD and 5-min recordings (mean Pearson ρ correlation coefficients of 0.913 and 0.944, respectively, and mean concordance correlation coefficients of 0.855 and 0.938, respectively). Associations were found between other ultra-short HRV parameters (SDNN, maximum RR, minimum RR, pNN50, ln(RMSSD) and 5-min recordings. In addition, average RR, HRV-TI, NN50, TP, LF/HF, ln(SDNN), ln(HRV-TI), ln(TP) and ln(LF/HF) from 1-min recordings were associated with 5-min values. In conclusion, some ultra-short HRV parameters can be used for ANS evaluation and presumably, for cardiovascular risk stratification among patients with dyslipidemia. These parameters seem to be of great practical value for both inpatient and outpatient settings, because most can be calculated from a standard 10-s ECG strip. The prognostic implications of ECG-derived, ultra-short HRV parameters in patients with dyslipidemia should be further evaluated in future studies.

Effects of combined histamine H1 and H2 receptor blockade on hemodynamic responses to dynamic exercise in males with high-normal blood pressure

While postexercise hypotension is associated with histamine H₁ and H₂ receptor-mediated postexercise vasodilation, effects of histaminergic vasodilation on blood pressure (BP) in response to dynamic exercise are not known. Thus, in 20 recreationally active male participants (10 normotensive and 10 with high-normal BP) we examined the effects of histamine H₁ and H₂ receptor blockade on cardiac output (CO), mean atrial pressure (MAP), aortic stiffness (AoStiff), and total vascular conductance (TVC) at rest and during progressive cycling exercise. Compared with the normotensive group, MAP, CO, and AoStiff were higher in the high-normal group before and after the blockade at rest, while TVC was similar. At the 40% workload, the blockade significantly increased MAP in both groups, while no difference was found in the TVC. CO was higher in the high-normal group than the normotensive group in both conditions. At the 60% workload, the blockade substantially increased MAP and decreased TVC in the normotensive group, while there were no changes in the high-normal group. A similar CO response pattern was observed at the 60% workload. These findings suggest that the mechanism eliciting an exaggerated BP response to exercise in the high-normal group may be partially due to the inability of histamine receptors. Novelty Males with high-normal BP had an exaggerated BP response to exercise. The overactive BP response is known due to an increase in peripheral vasoconstriction. Increase in peripheral vasoconstriction is partially due to inability of histamine receptors.

Acute Effect of Aerobic and Strength Exercise on Heart Rate Variability and Baroreflex Sensitivity in Men With Autonomic Dysfunction

de Paula, T, Neves, MF, da Silva Itaborahy, A, Monteiro, W, Farinatti, P, and Cunha, FA. Recovery pattern of cardiac autonomic control after aerobic and strength exercises in overweight prehypertensive men. J Strength Cond Res 33(10): 2743-2752, 2019-The extent to which postexercise cardiac autonomic control depends on exercise modality remains unclear, particularly among individuals with autonomic dysfunction (cardiac autonomic dysfunction [CADysf]). This study compared heart rate variability (HRV) and baroreflex sensitivity (BRS) responses to acute aerobic exercise (AE) and strength exercise (SE) in men with CADysf. Twenty men were assigned into control (n = 10: 33.8 ± 3.0 years; 23.7 ± 1.5 kg·m) and CADysf (n = 10: 36.2 ± 9.8 years; 28.4 ± 2.6 kg·m) groups. Cardiac autonomic dysfunction underwent AE, SE, and a nonexercise control day (control session [CTL]) in a randomized, counter-balanced order. Heart rate variability and BRS were assessed in a supine position during 25 minutes of recovery after AE, SE, and CTL. Both HRV indices (p ≤ 0.05; effect size [Cohen's d]: >1.4) and BRS at rest were significantly lower in CADysf than those in controls (p < 0.01; effect size [Cohen's d]: ≥1.36). In CADysf, postexercise increases in heart rate, sympathetic activity (low-frequency [LF] band), and sympathovagal balance (LF:high-frequency [HF] ratio), as well as decreases in R-R interval, parasympathetic activity (HF band), and BRS were observed in AE (p ≤ 0.05; effect size [Cohen's d]: ≥1.31) and SE (p ≤ 0.05; effect size [Cohen's d]: ≥0.79) vs. CTL, but changes were larger after AE than SE (p ≤ 0.05; effect size [Cohen's d]: ≥0.73). In conclusion, both AE and SE elicited postexercise changes in HRV and BRS among CADysf men, primarily reflected by lowered vagal modulation, increased sympathovagal balance, and a delayed BRS recovery pattern. However, those changes seem to be more likely to occur after AE than SE.

Heart rate variability and inflammation: A meta-analysis of human studies

The inflammatory reflex is known as the body's primary defense against infection and has been implicated in a number of diseases. The magnitude of the inflammatory response is important, as an extreme or insufficient response can be differentially harmful to the individual. Converging evidence suggests that the autonomic nervous system (ANS) regulates the inflammatory reflex. Heart rate variability (HRV) can be separated into components that primarily reflect parasympathetic (PNS) or vagal activity (i.e., indices of vagally mediated HRV) and a combination of both sympathetic (SNS) and PNS influences. Given the physiological relation between the vagus and inflammatory processes, one would expect to find higher HRV, especially indices of vagally-mediated HRV, to be associated with decreased levels of inflammation via the cholinergic anti-inflammatory pathway. However, existing findings here are mixed, such that studies have also shown a positive association between indices of HRV and markers of inflammation. Therefore, the present meta-analysis aimed to synthesize existing studies, estimating the general direction and strength of the relationship between different indices of HRV and inflammatory markers. A systematic search of the literature yielded 2283 studies that were screened for inclusion eligibility (159 studies eligible for inclusion); in sum, 51 studies reported/provided adequate information for inclusion in meta-analyses. Results generally showed negative associations between indices of HRV and markers of inflammation. In this regard, the standard deviation of R-R intervals (SDNN) and power in the high frequency band of HRV (HF-HRV) showed the strongest and most robust associations with inflammatory markers compared to other time- and frequency-domain measures of HRV. Overall, we propose that indices of HRV can be used to index activity of the neurophysiological pathway responsible for adaptively regulating inflammatory processes in humans.

The pathophysiology of complications after laparoscopic colorectal surgery: Role of baroreflex and chemoreflex impairment

INTRODUCTION

The aim of this study was to assess the dynamics of baroreflex sensitivity (BRS) during laparoscopic colorectal surgery in patients with different chemoreflex sensitivity assessed with breath-holding test.

METHODS

The study included 80 patients (mean age, 68 ± 7 years) who underwent routine laparoscopic colorectal surgery under general/epidural anaesthesia. Patients were retrospectively divided into two groups: with normal (breath-holding duration ≥38 s, group N [n = 42]) or high (breath-holding duration <38 s, group H [n = 38]) chemoreflex sensitivity. BRS was initially evaluated after arterial catheter placement before induction, after induction, after pneumoperitoneum, after extubation, and 6 h and 24 h after extubation.

RESULTS

Average BRS was significantly lower in the group with high peripheral chemoreflex sensitivity at all time points. The use of pneumoperitoneum did not significantly influence BRS in either group. After the surgery and 6 h after extubation, no significant changes were observed. After 6 h of the surgery, 11.9% of patients in group N and 57.8% of those in group H (p < 0.05) had severe baroreflex dysfunction (BRS < 3 ms/mmHg). After 24 h, only two patients in group N (vs 13 [34.2%] in group H, p < 0.05) had this dysfunction.

CONCLUSION

Patients with high chemoreflex sensitivity have lower BRS, and it decreases further after anaesthesia induction. The recovery process can take up to 24 h, with an increased risk of perioperative complications in patients with high preoperative chemoreflex sensitivity. The use of pneumoperitoneum does not significantly affect BRS.

Isolated Obesity Is Not Enough to Impair Cardiac Autonomic Modulation in Metabolically Healthy Men

PURPOSE

To evaluate whether excess body mass influences the heart rate variability (HRV) indexes at rest, and to correlate adiposity indicators and the aerobic fitness with cardiac autonomic variables in metabolically healthy young adults.

METHOD

In all, 41 untrained males (M_age = 21.80, SD = 2.14 years), 14 normal weight (M_BMI = 22.28, SD = 1.86 kg∙m^-2), 11 overweight (M_BMI = 26.95, SD = 1.43 kg∙m^-2), and 16 obese (M_BMI = 33.58, SD = 3.06 kg∙m^-2) metabolically healthy (normal values of blood pressure, fasting blood glucose, triglycerides, and total cholesterol), underwent evaluations of the HRV at rest and of the peak oxygen consumption (VO₂ peak) during maximal exercise on a cycle ergometer.

RESULTS

Blood pressure, heart rate, HRV indexes, casual blood glucose, oxidative stress, and antioxidant activity did not differ among the groups. The VO₂ peak (mL∙kg^-1∙min^-1) was lower in the obese group compared with the normal weight and overweight groups. The body mass (r = -.40 to -.45) and abdominal circumference (r = -.39 to -.52) were slightly to moderately correlated with SD1, SD2, RMSSD, SDNN, pNN50, LF, and HF indexes and total power. The VO₂ peak (mL∙kg^-1∙min^-1) was slightly to moderately correlated (r = .48 to .51) with SD2, SDNN, and LF indexes in the individuals with excess body mass.

CONCLUSION

Cardiac autonomic modulation at rest was preserved in metabolically healthy obese young men. However, the indicators of adiposity, as well as the aerobic fitness were correlated with cardiac autonomic modulation in the individuals with excess body mass.

Contribution of insulin resistance to decreased baroreceptor sensitivity & cardiometabolic risks in pre-obesity & obesity

Background & objectives:

Although insulin resistance (IR) is a known complication in obesity, the physiological mechanisms linking IR with cardiometabolic risks in obesity have not been well studied. This study was conducted to assess the difference in cardiovascular (CV) risk profile in IR and non-IR (NIR) conditions, and contribution of IR to cardiometabolic risks in pre-obese and obese individuals.

Methods:

Basal CV, blood pressure variability, autonomic function test and cardiometabolic parameters were recorded in pre-obese (n=86) and obese (n=77) individuals during 2012 and 2015. The association of altered cardiometabolic parameters with homeostatic model for IR (HOMA-IR) in pre-obese and obese groups and with baroreceptor sensitivity (BRS) in IR and NIR groups was calculated by appropriate statistical analysis.

Results:

Decreased BRS, a known CV risk and cardiometabolic parameters were significant in IR (pre-obese and obese) group compared to the NIR group. Sympathovagal imbalance in the form of increased sympathetic and decreased parasympathetic activities was observed in individuals with IR. There was no significant difference in the level of independent contribution of HOMA-IR to cardiometabolic parameters in pre-obese and obese groups. Adiponectin and inflammatory markers had an independent contribution to BRS in IR group.

Interpretation & conclusions:

Findings of the present study demonstrated that the intensity of cardiometabolic derangements and CV risk were comparable between IR, pre-obese and obese individuals. Pro-inflammatory state, dyslipidaemia and hypoadiponectinaemia might contribute to CV risk in these individuals with IR. IR could possibly be the link between altered metabolic profile and increased CV risks in these individuals independent of the adiposity status.

Total and differential white blood cell counts and hemodynamic parameters in first-episode psychosis

There is evidence for blood inflammatory abnormalities in patients with first-episode psychosis (FEP). The monocyte- and neutrophil-to-lymphocyte ratios (MLR; NLR) are markers of inflammation and endothelial dysfunction, and predictors of cardiovascular disease, the leading cause of death in schizophrenia. We investigated relationships between white blood cell (WBC) counts and hemodynamic parameters associated with cardiovascular disease risk in 25 subjects age 18-50 hospitalized for FEP and 44 controls. Subjects had a blood draw, vital signs, and medical history. Patients with FEP had significantly higher NLR, MLR, pulse pressure, and rate pressure product (RPP) than controls (p < 0.05 for each), after controlling for potential confounders. In linear regression analyses, higher monocytes were a significant predictor of higher pulse pressure (p = 0.033) and higher MLR predicted RPP at the trend level (p = 0.051) in FEP, after controlling for potential confounders. To our knowledge, ours is the first report of increased RPP, a measure of myocardial workload, in FEP. We also replicated findings of increased NLR, MLR and pulse pressure in FEP. Our findings underscore that measurement of routine vital signs and blood total and differential WBC counts are germane to the clinical care of patients with psychosis as markers of cardiovascular disease risk.

Autonomic function testing: Compliance and consequences

BACKGROUND

The deep breathing test (DB) and Valsalva maneuver (VM) are used to detect autonomic dysfunction. The VM induces sympathetically mediated changes in blood pressure (phase II late, phase IV, and recovery time) and both tests induce vagally mediated heart rate changes. There is limited information on effects of key variables, compliance with testing and the effects of non-compliance This study has twin goals of evaluating compliance with standard instructions and the effects of changes in key variables. We also evaluated the effect of position on the VM.

MATERIAL AND METHODS

Forty healthy males performed DB at air exchange volumes of 50, 80, and 100% of vital lung capacity (VLC). The VM was performed at 40 and 30mmHg expiratory pressure for 15 and 10s in sitting and supine position, respectively.

RESULTS

Participants performed DB at lower volumes than intended and were not able to maintain 100% VLC for the duration of the test. The DB heart rate response decreased 6.3beats/min per liter below VLC. During the VM, subjects blew at lower pressures than instructed. The VM responses were significantly larger with longer expiration durations, higher expiratory pressures and when performed sitting. Performing the VM at 40mmHg for 10s in supine position increased the odds ratio of experiencing flat-top responses.

CONCLUSION

The ability of subjects to strictly comply with methodological guidelines significantly improves results. Recording of both test parameters and ensuing results is suggested.

Association of Sympathovagal Imbalance With Cognitive Impairment in Type 2 Diabetes in Adults

OBJECTIVE

Sympathovagal imbalance (SVI) has been reported to be associated with metabolic derangements in type 2 diabetes. We investigated the association of SVI with cognitive impairment in patients with type 2 diabetes.

METHODS

Patients with a new diagnosis of type 2 diabetes (n=43) and age-matched healthy control subjects (n=43) were recruited for the study. Body mass index and blood pressure measurements were recorded. SVI was assessed by spectral analysis of heart rate variability (HRV), and cognitive function was assessed by recording the positive wave that appears in 300 milliseconds from application of stimulus in event-related potential tracing (P300). Insulin resistance was determined by the homeostatic model assessment of insulin resistance (HOMA-IR) formula using blood glucose and insulin data, and oxidative stress was assessed by estimation of malondialdehyde. Association of various factors with cognitive impairment was evaluated by Pearson correlation analysis, and independent contributions of these factors to cognitive impairment were assessed by multiple regression analysis.

RESULTS

P300 latency was significantly prolonged in the diabetes group compared with the control group. Ratio of low-frequency to high-frequency power (LF-HF ratio) of HRV, the marker of SVI was found to be significantly correlated and linked with P300. Malondialdehyde and HOMA-IR were correlated with LF-HF ratio.

CONCLUSION

Treatment-naïve patients with type 2 diabetes have SVI and considerable cognitive impairment. Insulin resistance and oxidative stress contribute to cognitive impairment, and SVI could be the physiologic link to cognitive impairment in treatment-naïve patients with type 2 diabetes.

Hyperinsulinemia and obese phenotype differently influence blood pressure in young normotensive patients with polycystic ovary syndrome

To differentiate the impact of insulin levels/resistance per se from that of excess weight on blood pressure (BP) daily changes, we evaluated, using 24-h ambulatory blood pressure monitoring (ABPM), systolic blood pressure (SBP) and diastolic blood pressure (DBP) in a cohort of young normotensive patients affected by polycystic ovary syndrome (PCOS). A cross-sectional study was performed. Fifty-four patients were studied according to (a) insulinemic state: 32 hyperinsulinemic and/or insulin-resistant (h-INS) and 22 normoinsulinemic (n-INS) patients; and (b) body mass index (BMI): 22 obese (BMI > 30) and 32 lean (18.0 < BMI < 24.9) patients. Each subject's SBP and DBP and heart rate (HR) were measured by ABPM. Supine and upright plasma renin activity (PRA), and aldosterone levels were also assayed. Patients in the h-INS group showed higher 24-h, daytime, and nighttime diastolic blood pressure (DBP), higher nighttime systolic blood pressure (SBP) levels, as well as an increased 24-h, daytime and nighttime HR, compared to both obese and lean patients in the n-INS group. In relation to BMI, only 24-h, daytime, and nighttime DBP were higher in obese than in lean patients. At variance, when both h-INS and obesity were considered, 24-h SBP and DBP were higher in h-INS obese subjects than in the other groups. In multivariate analysis, insulin (max peak), area under the curve of insulin and insulin sensitivity index was independently associated with SBP. (1) Within a normotensive range, hyperinsulinemia and/or insulin resistance influence daily BP variation more than obesity does, suggesting a pivotal role of insulin on BP control in PCOS; (2) altered insulinemic state and ABPM-derived higher nighttime BP and HR may represent early markers to identify PCOS subjects prone to high cardiovascular risk.

Decreased baroreflex sensitivity is linked to sympathovagal imbalance, low-grade inflammation, and oxidative stress in pregnancy-induced hypertension

Pregnancy-induced hypertension (PIH) has been reported as a cardiovascular (CV) risk. We assessed the sympathovagal imbalance (SVI) and the association of inflammation and oxidative stress (OS) with CV risks in PIH. A total of 125 pregnant women having a risk factor for PIH were followed till term and the incidence of PIH was observed. Retrospectively, they were divided into two groups: Group I (those who did not develop PIH, n = 82) and Group II (those who developed PIH, n = 43). Blood pressure variability (BPV) parameters including baroreflex sensitivity (BRS), spectral heart rate variability (HRV), autonomic function tests (AFTs), inflammatory markers (interleukin-6, TNF-α, interferon-γ), and OS markers were measured in both the groups. Alterations in parasympathetic and sympathetic components of AFTs were analyzed. Link of various parameters to BRS was assessed by correlation and multiple regression analysis. Parasympathetic components of AFTs were decreased from the early part of pregnancy and sympathetic components were increased toward the later part of pregnancy. Decreased BRS, the marker of CV risk, was more prominent in Group II subjects. Independent contribution of interleukin-6 (β = 0.276, P = 0.020), TNF-α (β = 0.408, P = 0.002), interferon-γ (β = 0.355, P = 0.008), and thiobarbituric-acid reactive substance (β = 0.287, P = 0.015) to BRS was found to be significant. It was concluded that sympathetic overactivity that develops more in the later part (third trimester) of pregnancy contributes to SVI and genesis of PIH. In PIH women, CV risks are present from the beginning of pregnancy that intensifies in the later part of pregnancy. Retrograde inflammation and oxidative stress contribute to the decreased BRS in PIH.

Acute cyclooxygenase inhibition and baroreflex sensitivity in lean and obese adults

PURPOSE

Obese adults exhibit increased levels of inflammation, which may negatively affect blood pressure regulation. Based on existing literature, we hypothesized: (1) baroreflex sensitivity would be lower in obese adults when compared to lean adults; (2) acute ibuprofen (IBU, a cyclooxygenase inhibitor and nonsteroidal antiinflammatory agent) administration would increase baroreflex sensitivity in obese adults, with no effect in lean adults.

METHODS

Seven lean (4 male, 3 female) and six obese (5 M, 1 F) adults completed two visits randomized to control (CON) or IBU (800 mg oral). On each visit, blood pressure (intra-arterial catheter), heart rate (ECG), and muscle sympathetic nerve activity (MSNA, microneurography) were measured continuously. Sympathetic and cardiac baroreflex sensitivities were assessed using the modified Oxford technique.

RESULTS

Measures of systemic inflammation [C-reactive protein (CRP) and interleukin-6 (IL-6)] were higher in obese adults when compared to lean adults and tended to decrease with IBU (IL-6: p < 0.05; CRP: p = 0.14). Cardiac baroreflex sensitivity was lower in obese adults (14 ± 2 vs. 24 ± 2 ms/mmHg, p = 0.02), whereas sympathetic baroreflex sensitivity was higher in obese adults (-3.6 ± 0.5 vs. -2.1 ± 0.5 bursts/100 beats/mmHg, p = 0.03) when compared to lean. There was no effect of IBU on cardiac or sympathetic baroreflex sensitivity in either group (p value range 0.20-0.71).

CONCLUSION

Despite obese individuals exhibiting higher levels of systemic inflammation and lower cardiac baroreflex sensitivity when compared to lean adults, an acute dose of IBU has no effect on cardiac or sympathetic baroreflex sensitivity.

Sex differences in associations between insulin resistance, heart rate variability, and arterial stiffness in healthy women and men: a physiology study

Diabetes confers greater cardiovascular risk to women than to men. Whether insulin-resistance-mediated risk extends to the healthy population is unknown. Measures of insulin resistance (fasting insulin, homeostatic model assessment, hemoglobin A1c, quantitative insulin sensitivity check index, glucose) were determined in 48 (56% female) healthy subjects. Heart rate variability (HRV) was calculated by spectral power analysis and arterial stiffness was determined using noninvasive applanation tonometry. Both were measured at baseline and in response to angiotensin II infusion. In women, there was a non-statistically significant trend towards increasing insulin resistance being associated with an overall unfavourable HRV response and increased arterial stiffness to the stressor, while men demonstrated the opposite response. Significant differences in the associations between insulin resistance and cardiovascular physiological profile exist between healthy women and men. Further studies investigating the sex differences in the pathophysiology of insulin resistance in cardiovascular disease are warranted.

Endothelial nitric oxide synthase gene polymorphisms are associated with cardiovascular risks in prehypertensives

Though endothelial nitric oxide synthase (eNOS) gene polymorphism is documented in the causation of hypertension, its role in prehypertension has not been investigated. The present study was conducted in 172 subjects divided into prehypertensives (n = 57) and normotensives (n = 115). Cardiovascular (CV) parameters including baroreflex sensitivity (BRS) by continuous BP variability assessment and sympathovagal imbalance (SVI) by heart rate variability analysis were recorded. Biochemical parameters for insulin resistance (homeostatic model for assessment of insulin resistance), oxidative stress, lipid risk factors, renin, and inflammatory parameters were measured. Genotyping for eNOS polymorphisms rs1799983 (298G>T) and rs2070744 (-786T>C) was performed by polymerase chain reaction-restriction fragment length polymorphism method. Multiple regression analysis was done to assess the association between SVI and metabolic markers, and multivariate logistic regression was done to determine the prediction of prehypertension status by genotype, BRS, and ratio of low-frequency to high-frequency in these subjects. The BP variability, heart rate variability, and biochemical parameters were significantly altered in prehypertensives. The eNOS polymorphisms were found to be associated with prehypertension. BRS, the marker of SVI, was significantly associated with BP, homeostatic model for assessment of insulin resistance, and tumor necrosis factor alpha in 298GG genotype of prehypertensive population. The eNOS gene polymorphisms appear to be associated with prehypertension. 298G>T and -786T>C contribute to SVI in young prehypertensives attributed by insulin resistance and inflammation. The CV risks were associated with prehypertension status in prehypertensives expressing both 298GG and -786TT genotypes. Association of CV risks with SVI appears to be stronger in prehypertensives expressing GG genotype.

The type of the functional cardiovascular response to upright posture is associated with arterial stiffness: a cross-sectional study in 470 volunteers

BACKGROUND

In a cross-sectional study we examined whether the haemodynamic response to upright posture could be divided into different functional phenotypes, and whether the observed phenotypes were associated with known determinants of cardiovascular risk.

METHODS

Volunteers (n = 470) without medication with cardiovascular effects were examined using radial pulse wave analysis, whole-body impedance cardiography, and heart rate variability analysis. Based on the passive head-up tilt induced changes in systemic vascular resistance and cardiac output, the principal determinants of blood pressure, a cluster analysis was performed.

RESULTS

The haemodynamic response could be clustered into 3 categories: upright increase in vascular resistance and decrease in cardiac output were greatest in the first (+45 % and -27 %, respectively), smallest in the second (+2 % and -2 %, respectively), and intermediate (+22 % and -13 %, respectively) in the third group. These groups were named as 'constrictor' (n = 109), 'sustainer' (n = 222), and 'intermediate' (n = 139) phenotypes, respectively. The sustainers were characterized by male predominance, higher body mass index, blood pressure, and also by higher pulse wave velocity, an index of large arterial stiffness, than the other groups (p < 0.01 for all). Heart rate variability analysis showed higher supine and upright low frequency/high frequency (LF/HF) ratio in the sustainers than constrictors, indicating increased sympathovagal balance. Upright LF/HF ratio was also higher in the sustainer than intermediate group. In multivariate analysis, independent explanatory factors for higher pulse wave velocity were the sustainer (p < 0.022) and intermediate phenotypes (p < 0.046), age (p < 0.001), body mass index (p < 0.001), and hypertension (p < 0.001).

CONCLUSIONS

The response to upright posture could be clustered to 3 functional phenotypes. The sustainer phenotype, with smallest upright decrease in cardiac output and highest sympathovagal balance, was independently associated with increased large arterial stiffness. These results indicate an association of the functional haemodynamic phenotype with an acknowledged marker of cardiovascular risk.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01742702.

Do Patient Profiles Influence the Effects of Massage? A Controlled Clinical Trial

Considerable scientific evidence has been published on the effectiveness of massage in different conditions, but it remains unclear whether this effectiveness is modulated by the profile of patients. The aim of this study was to compare the effects of a 21-min myofascial therapy protocol on stress responders and nonresponders stressed in the laboratory with a cold pressor test. Dependent variables included heart rate variability (HRV), blood pressure, and salivary markers such as flow rate, cortisol, immunoglobulin A (IgA), and α-amylase activity. A controlled, repeated measures, single-blind trial was conducted in 30 Caucasian students with a mean (SD) age of 20.70 (4.50) years. We found no significant between-group differences in descriptive characteristics or in any preintervention outcome measure. Analysis of covariance revealed significant increases in HRV index (F = 0.18, p = .01), salivary flow rate (F = 0.16, p = .02), and salivary IgA concentration (F = 4.36, p = .04) and significant decreases in the low-frequency domain (F = 0.18, p = .04) and LF-high-frequency ratio (F = 0.18, p = .01) in the stress responder group in comparison to the nonresponder group. In conclusion, a better response to massage was observed in stress responders than in nonresponders across various HRV parameters and salivary measures.

Cardiovascular and metabolic risk markers are related to parasympathetic indices in pre-pubertal adolescents

OBJECTIVE

To analyse the relationship between different heart rate variability indices, resting heart rate, and cardiovascular markers in adolescents.

METHODS

A cross-sectional study was carried out with information from an ongoing cohort study. The sample was composed of 99 adolescents who complied with the following inclusion criteria: aged between 11 and 14 years; enrolled in a school unit of elementary education; absence of any known diseases; no drug consumption; and a formal consent signed by the parents or legal guardians. Weight, height, heart rate variability, lipid profile, inflammatory markers, blood pressure, resting heart rate, intima-media thickness, blood flow, and trunk fatness were measured. Partial correlation and linear regression (expressed by β and 95% confidence intervals [95%CI]) analyses were used to analyse the relationships between the variables.

RESULTS

In the linear regression analysis, even after adjustments for sex, age, trunk fatness, and somatic maturation, parasympathetic activity presented significant correlations with maximum carotid artery blood flow (β=-0.111 [95%CI=-0.216; -0.007]), systolic blood pressure (β=-0.319 [95%CI=-0.638; -0.001]), and resting heat rate (β=-0.005 [95%CI=-0.009; -0.002]).

CONCLUSION

Parasympathetic activity at rest is inversely related to maximum and minimum blood flow, triacylglycerol levels, and systolic blood pressure. These findings suggest that heart rate variability has the potential to discriminate pre-pubertal adolescents at increased risk.

A device for co-culturing autonomic neurons and cardiomyocytes using micro-fabrication techniques

We developed a device for co-culturing sympathetic neurons, parasympathetic neurons, and cardiomyocytes using micro-fabrication techniques.

Toll-like receptor 9 plays a key role in the autonomic cardiac and baroreflex control of arterial pressure

The crosstalk between the immune and the autonomic nervous system may impact the cardiovascular function. Toll-like receptors are components of the innate immune system and play developmental and physiological roles. Toll-like receptor 9 (TLR9) is involved in the pathogenesis of cardiovascular diseases, such as hypertension and heart failure. Since such diseases are commonly accompanied by autonomic imbalance and lower baroreflex sensitivity, we hypothesized that TLR9 modulates cardiac autonomic and baroreflex control of arterial pressure (AP). Toll-like receptor 9 knockout (TLR9 KO) and wild-type (WT) mice were implanted with catheters into carotid artery and jugular vein and allowed to recover for 3 days. After basal recording of AP, mice received methyl-atropine or propranolol. AP and pulse interval (PI) variability were evaluated in the time and frequency domain (spectral analysis), as well as by multiscale entropy. Spontaneous baroreflex was studied by sequence technique. Behavioral and cardiovascular responses to fear-conditioning stress were also evaluated. AP was similar between groups, but TLR9 KO mice exhibited lower basal heart rate (HR). AP variability was not different, but PI variability was increased in TLR9 KO mice. The total entropy was higher in TLR9 KO mice. Moreover, baroreflex function was found higher in TLR9 KO mice. Atropine-induced tachycardia was increased in TLR9 KO mice, whereas the propranolol-induced bradycardia was similar to WT mice. TLR9 KO mice exhibit increased behavioral and decreased tachycardia responses to fear-conditioning stress. In conclusion, our findings suggest that TLR9 may negatively modulate cardiac vagal tone and baroreflex in mice.