IDENTIFICATION OF BLOOD PRESSURE CONTROL MECHANISMS BY POWER SPECTRAL ANALYSIS

Changes in cardiovascular autonomic control induced by chronic inhibition of acetylcholinesterase during pyridostigmine or donepezil treatment of spontaneously hypertensive rats

Chronic treatment with acetylcholinesterase inhibitors may be a promising therapeutic strategy for treatment of cardiovascular diseases. The aim of our study was to analyze the changes in blood pressure (BP) and heart rate (HR) during 14 days of treatment with two different acetylcholinesterase inhibitors - pyridostigmine (PYR) having only peripheral effects or donepezil (DON) with both peripheral and central effects. In addition, we studied their effects on the cardiovascular response to restraint stress and on sympathovagal control of HR in normotensive Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR). SHR were characterized by elevated BP and increased low-frequency component of systolic BP variability (LF-SBPV), but their cardiac vagal tone and HR variability (HRV) were reduced compared with WKY. Chronic treatment with either acetylcholinesterase inhibitor decreased HR and increased HRV in both strains. PYR treatment slightly decreased BP and LF-SBPV in the dark phase of the day. Neither drug significantly altered BP response to stress, but PYR attenuated HR increase during restraint stress. Regarding sympathovagal balance, acute methylatropine administration caused a greater increase of HR in WKY than in SHR. Chronic PYR or DON treatment enhanced HRV and HR response to methylatropine (vagal tone) in WKY, whereas PYR but not DON treatment potentiated HRV and vagal tone in SHR. In conclusion, vagal tone was lower in SHR compared with WKY, but was enhanced by chronic PYR treatment in both strains. Thus, chronic peripheral, but not central, acetylcholinesterase inhibition has major effects on HR and its variability in both normotensive and hypertensive rats.

CVRanalysis: a free software for analyzing cardiac, vascular and respiratory interactions

Introduction: Simultaneous beat-to-beat R-R intervals, blood pressure and respiration signals are routinely analyzed for the evaluation of autonomic cardiovascular and cardiorespiratory regulations for research or clinical purposes. The more recognized analyses are i) heart rate variability and cardiac coherence, which provides an evaluation of autonomic nervous system activity and more particularly parasympathetic and sympathetic autonomic arms; ii) blood pressure variability which is mainly linked to sympathetic modulation and myogenic vascular function; iii) baroreflex sensitivity; iv) time-frequency analyses to identify fast modifications of autonomic activity; and more recently, v) time and frequency domain Granger causality analyses were introduced for assessing bidirectional causal links between each considered signal, thus allowing the scrutiny of many physiological regulatory mechanisms. Methods: These analyses are commonly applied in various populations and conditions, including mortality and morbidity predictions, cardiac and respiratory rehabilitation, training and overtraining, diabetes, autonomic status of newborns, anesthesia, or neurophysiological studies. Results: We developed CVRanalysis, a free software to analyze cardiac, vascular and respiratory interactions, with a friendly graphical interface designed to meet laboratory requirements. The main strength of CVRanalysis resides in its wide scope of applications: recordings can arise from beat-to-beat preprocessed data (R-R, systolic, diastolic and mean blood pressure, respiration) or raw data (ECG, continuous blood pressure and respiratory waveforms). It has several tools for beat detection and correction, as well as setting of specific areas or events. In addition to the wide possibility of analyses cited above, the interface is also designed for easy study of large cohorts, including batch mode signal processing to avoid running repetitive operations. Results are displayed as figures or saved in text files that are easily employable in statistical softwares. Conclusion: CVRanalysis is freely available at this website: anslabtools.univ-st-etienne.fr. It has been developed using MATLAB® and works on Windows 64-bit operating systems. The software is a standalone application avoiding to have programming skills and to install MATLAB. The aims of this paper area are to describe the physiological, research and clinical contexts of CVRanalysis, to introduce the methodological approach of the different techniques used, and to show an overview of the software with the aid of screenshots.

Changes in beat-to-beat blood pressure and pulse rate variability following stroke

Associations between cerebrovascular disease and impaired autonomic function and cerebrovascular reactivity have led to increased interest in variability of heart rate (HRV) and blood pressure (BPV) following stroke. In this study, beat-to-beat pulse rate variability (PRV) and BPV were measured in clinically stable stroke patients (6 ischemic, 2 hemorrhagic) at least one year after their last cerebrovascular event. Beat-to-beat blood pressure (BP) measurements were collected from subjects while resting in the sitting position for one hour. Compared with healthy controls, stroke patients exhibited significantly greater time-domain (standard deviation, coefficient of variation, average real variability) and normalized high-frequency BPV (all p < 0.05). Stroke patients also exhibited lower LF:HF ratios than control subjects (p = 0.003). No significant differences were observed in PRV between the two groups, suggesting that BPV may be a more sensitive biomarker of cerebrovascular function in long-term post-stroke patients. Given a paucity of existing literature investigating beat-to-beat BPV in clinically stable post-stroke patients long (> 1 year) after their cerebrovascular events, this pilot study can help inform future studies investigating the mechanisms and effects of BPV in stroke. Elucidating this physiology may facilitate long-term patient monitoring and pharmacological management to mitigate the risk for recurrent stroke.

Baroreflex sensitivity following acute upper-body exercise in the cold among stable coronary artery disease patients

Background: A cold environment and exercise separately affect the autonomic nervous system (ANS), baroreflex sensitivity (BRS), and blood pressure variability (BPV) but their combined effects on post-exercise recovery are not known. Our cross-over trial examined these responses following upper-body static and dynamic exercise performed in a cold and neutral environment in patients with coronary artery disease (CAD). Methods: 20 patients with stable coronary artery disease performed both graded static (10%-30% of maximal voluntary contraction) and dynamic (light, moderate and high perceived intensity) upper-body exercise at -15°C and +22°C for 30 min. Electrocardiogram and continuous blood pressure were measured to compute post-exercise (10 and 30 min after exercise) spectral powers of heart rate (HR), blood pressure variability and BRS at low (0.04-0.15 Hz) and high (0.15-0.4 Hz) frequencies. Results: Static upper-body exercise performed in a cold environment increased post-exercise high frequency (HF) spectral power of heart rate (HF RR) (p < 0.001) and reduced heart rate (p = 0.001) and low-to-high frequency (LF/HF) ratio (p = 0.006) more than in a neutral environment. In addition, post-exercise mean BRS (p = 0.015) and high frequency BRS (p = 0.041) increased more following static exercise in the cold than in a neutral environment. Dynamic upper-body exercise performed in a cold environment reduced post-exercise HF BRS (p = 0.019) and systolic blood pressure (p = 0.003). Conclusion: Static upper-body exercise in the cold increased post-exercise BRS and overall vagal activity but without reduced systolic blood pressure. Dynamic upper-body exercise in the cold reduced post-exercise vagal BRS but did not affect the other parameters. The influence of cold exposure on post-exercise autonomic and cardiovascular responses following static upper-body exercise require further studies. This information helps understanding why persons with cardiovascular diseases are vulnerable to low environmental temperature. ClinicalTrials.gov: NCT02855905 (04/08/2016).

Glyceryl trinitrate-induced blood pressure variability decrease during head-up tilt test predicts vasovagal response

PURPOSE

Glyceryl trinitrate (GTN) provoked cardioinhibitory syncope during the head-up tilt test is preceded by a period of disrupted blood pressure variability (BPV). Endogenous nitric oxide (NO) attenuates BPV independently of blood pressure (BP). We hypothesized that exogenous NO donor GTN might decrease BPV during the presyncope period. A decrease in BPV may predict the tilt outcome.

METHODS

We analyzed 29 tilt test recordings of subjects with GTN-induced cardioinhibitory syncope and 30 recordings of negative subjects. A recursive autoregressive model of BPV after GTN was performed; powers of the respiratory (0.15-0.45 Hz) and nonrespiratory frequency (0.01-0.15 Hz) bands were calculated for each of the 20 normalized time periods. The post-GTN relative changes in heart rate, BP, and BPV were calculated.

RESULTS

In the syncope group, spectral power of nonrespiratory frequency systolic and diastolic BPV progressively felt for 30% after GTN application and stabilized after 180 s. BP started to fall 240 s after the GTN application. Decrease in nonrespiratory frequency power of diastolic BPV 20 s after GTN administration predicted cardioinhibitory syncope (area under the curve 0.811; 77% sensitivity; 70% specificity; cutoff value > 7%).

CONCLUSION

GTN application during the tilt test attenuates systolic and diastolic nonrespiratory frequency BPV during the presyncope period, independent of BP. A decrease in nonrespiratory frequency diastolic BPV 20 s after GTN application predicts cardioinhibitory syncope with good sensitivity and moderate specificity.

Association between Daytime Sleepiness, Fatigue and Autonomic Responses during Head-Up Tilt Test in Multiple Sclerosis Patients

We aimed to assess dynamic changes in hemodynamic and autonomic function in response to the head-up tilt test (HUTT) in patients with multiple sclerosis (MS) compared to healthy controls (HCs) and evaluate its relationship with the patients' reported daytime sleepiness and fatigue symptoms. A total of 58 MS patients and 30 HCs were included in the analysis. Fatigue and sleepiness were evaluated using the Chalder Fatigue Scale (CFQ) and the Epworth Sleepiness Scale (ESS), respectively. Hemodynamic response, baroreflex sensitivity, heart rate variability, and systolic and diastolic blood pressure (BP) variability (SBPV, DBPV) parameters were calculated at rest, and in response to the HUTT. The MS patients displayed attenuated BP responses coupled with a more pronounced decrease in cardiac index as well as a reduced increase in the low frequency (LFnu) of DBPV (p = 0.021) and the sympathovagal ratio (p = 0.031) in the latter-phase orthostatic challenge compared to HCs. In MS patients, the ESS score showed no correlation with CFQ or clinical disease outcomes, but exhibited a moderate correlation with LFnu of BPVrest. Fatigue and disease variants predicted blood pressure response to HUTT. These findings underscore the importance of subjective daytime sleepiness and fatigue symptoms and their role in blood pressure regulation in MS patients.

Genetic Ablation of Prorenin Receptor in the Rostral Ventrolateral Medulla Influences Blood Pressure and Hydromineral Balance in Deoxycorticosterone-Salt Hypertension

Non-enzymatic activation of renin via its interaction with prorenin receptor (PRR) has been proposed as a key mechanism of local renin-angiotensin system (RAS) activation. The presence of renin and angiotensinogen has been reported in the rostral ventrolateral medulla (RVLM). Overactivation of bulbospinal neurons in the RVLM is linked to hypertension (HTN). Previous studies have shown that the brain RAS plays a role in the pathogenesis of the deoxycorticosterone (DOCA)-salt HTN model. Thus, we hypothesized that PRR in the RVLM is involved in the local activation of the RAS, facilitating the development of DOCA-salt HTN. Selective PRR ablation targeting the RVLM (PRRRVLM-Null mice) resulted in an unexpected sex-dependent and biphasic phenotype in DOCA-salt HTN. That is, PRRRVLM-Null females (but not males) exhibited a significant delay in achieving maximal pressor responses during the initial stage of DOCA-salt HTN. Female PRRRVLM-Null subsequently showed exacerbated DOCA-salt-induced pressor responses during the "maintenance" phase with a maximal peak at 13 d on DOCA-salt. This exacerbated response was associated with an increased sympathetic drive to the resistance arterioles and the kidney, exacerbated fluid and sodium intake and output in response to DOCA-salt, and induced mobilization of fluids from the intracellular to extracellular space concomitant with elevated vasopressin. Ablation of PRR suppressed genes involved in RAS activation and catecholamine synthesis in the RVLM but also induced expression of genes involved in inflammatory responses. This study illustrates complex and sex-dependent roles of PRR in the neural control of BP and hydromineral balance through autonomic and neuroendocrine systems. Graphical abstract.

Effect of Yoga Based Cardiac Rehabilitation on Blood Pressure Variability and Baroreflex Sensitivity: RCT in Patients Post MI

To assess the effects of 12 weeks Yoga based Cardiac Rehabilitation program on Blood Pressure Variability and Baroreflex Sensitivity in Eighty patients post myocardial infarction. Randomized controlled trial with two parallel groups. A tertiary care institution in India. The Yoga group received 13 hospital-based structured yoga sessions in adjunct to the standard care. Control Group participants received enhanced standard care involving three brief educational sessions on importance of diet and physical activity. Beat to beat arterial pressure variability and baroreflex sensitivity was determined non-invasively. Baseline measurement was done at 3 weeks post Myocardial Infarction. The measurements were repeated at 13th week and at 26th week post MI. There was no significant difference between the groups in time domain indices of SBP variability. At 26th week post MI, after normalization the Low Frequency power increased in the yoga group as compared to the decrease in the standard care group (p = 0.02). Though the High Frequency power increased in both the groups, the magnitude of increase was higher in the standard care group (p = 0.005). However, the total power increased significantly in yoga group with a concurrent decrease in standard care group (p =  < 0.001). The SBP All BRS was significantly different between the groups with an increase in the yoga group and a decline in standard care group (p = 0.003) at 13th week. A short-term Yoga based cardiac rehabilitation has additive effects in improving baroreflex sensitivity and dampening blood pressure variability post myocardial infarction in patients under optimal medication.The main trial is registered in Clinical Trials Registry-India (CTRI) (Ref. No: CTRI/2012/02/002408). In addition, CTRI has also been registered for the sub-study. (Ref. No: CTRI/2017/09/009925).

Hypertension in chronic kidney disease: What lies behind the scene

Hypertension is a frequent condition encountered during kidney disease development and a leading cause in its progression. Hallmark factors contributing to hypertension constitute a complexity of events that progress chronic kidney disease (CKD) into end-stage renal disease (ESRD). Multiple crosstalk mechanisms are involved in sustaining the inevitable high blood pressure (BP) state in CKD, and these play an important role in the pathogenesis of increased cardiovascular (CV) events associated with CKD. The present review discusses relevant contributory mechanisms underpinning the promotion of hypertension and their consequent eventuation to renal damage and CV disease. In particular, salt and volume expansion, sympathetic nervous system (SNS) hyperactivity, upregulated renin–angiotensin–aldosterone system (RAAS), oxidative stress, vascular remodeling, endothelial dysfunction, and a range of mediators and signaling molecules which are thought to play a role in this concert of events are emphasized. As the control of high BP via therapeutic interventions can represent the key strategy to not only reduce BP but also the CV burden in kidney disease, evidence for major strategic pathways that can alleviate the progression of hypertensive kidney disease are highlighted. This review provides a particular focus on the impact of RAAS antagonists, renal nerve denervation, baroreflex stimulation, and other modalities affecting BP in the context of CKD, to provide interesting perspectives on the management of hypertensive nephropathy and associated CV comorbidities.

Stratified Multivariate Multiscale Dispersion Entropy for Physiological Signal Analysis

Multivariate entropy quantification algorithms are becoming a prominent tool for the extraction of information from multi-channel physiological time-series. However, in the analysis of physiological signals from heterogeneous organ systems, certain channels may overshadow the patterns of others, resulting in information loss. Here, we introduce the framework of Stratified Entropy to prioritize each channels' dynamics based on their allocation to respective strata, leading to a richer description of the multi-channel time-series. As an implementation of the framework, three algorithmic variations of the Stratified Multivariate Multiscale Dispersion Entropy are introduced. These variations and the original algorithm are applied to synthetic time-series, waveform physiological time-series, and derivative physiological data. Based on the synthetic time-series experiments, the variations successfully prioritize channels following their strata allocation while maintaining the low computation time of the original algorithm. In experiments on waveform physiological time-series and derivative physiological data, increased discrimination capacity was noted for multiple strata allocations in the variations when benchmarked to the original algorithm. This suggests improved physiological state monitoring by the variations. Furthermore, our variations can be modified to utilize a priori knowledge for the stratification of channels. Thus, our research provides a novel approach for the extraction of previously inaccessible information from multi-channel time series acquired from heterogeneous systems.

The potential therapeutic benefits of low frequency haemodynamic oscillations

Haemodynamic oscillations occurring at frequencies below the rate of respiration have been observed experimentally for more than a century. Much of the research regarding these oscillations, observed in arterial pressure and blood flow, has focused on mechanisms of generation and methods of quantification. However, examination of the physiological role of these oscillations has been limited. Multiple studies have demonstrated that oscillations in arterial pressure and blood flow are associated with the protection in tissue oxygenation or functional capillary density during conditions of reduced tissue perfusion. There is also evidence that oscillatory blood flow can improve clearance of interstitial fluid, with a growing number of studies demonstrating a role for oscillatory blood flow to aid in clearance of debris from the brain. The therapeutic potential of these haemodynamic oscillations is an important new area of research which may have beneficial impact in treating conditions such as stroke, cardiac arrest, blood loss injuries, sepsis, or even Alzheimer's disease and vascular dementia.

Blood pressure variability is altered in secondary progressive multiple sclerosis but not in patients with a clinically isolated syndrome

OBJECTIVES

To investigate differences in beat-to-beat systolic blood pressure variability (SBPV) in people with secondary progressive MS (pwSPMS), clinically isolated syndrome (pwCIS) and healthy controls (HC).

METHODS

This retrospective case-control study included 46 pwSPMS, 46 pwCIS and 44 HC. A semi-automated software made with MATLAB R2019b (The MathWorks, Inc.) was used for the evaluation of SBPV. The frequency domain characteristics observed were the power spectrum in the LF and HF bands and the LF/HF ratio. Data is expressed in absolute power (mmHg²) of LF and HF and ratio (LF/HF) during both supine and tilt-up phases of testing.

RESULTS

There were no significant differences in mean systolic (sBP) or diastolic blood pressure (dBP) values during supine and tilt-up phases of testing between groups. During the supine phase of testing LF and LF/HF were significantly lower in the SPMS group (4.17±5.38 and 3.52±2.34, respectively) compared to the CIS (5.42±3.59, p = 0.015 and 5.92±4.63, p = 0.029, respectively) and HC group (6.03±4.55, p = 0.011 and 6.52 ± 5.09, p = 0.010, respectively), while during the tilt-up phase, LF was significantly lower compared to both the CIS and HC group, and HF was significantly lower only compared to the CIS group.

CONCLUSION

SBPV is altered in pwSPMS compared to pwCIS and normal controls. Further research in the field of MS related dysautonomia is warranted not only because of its relevance to comorbidities and MS symptoms, but also because of its likely involvement in the pathophysiology of MS.

Blood Pressure Variability Indices for Outcome Prediction After Thrombectomy in Stroke by Using High-Resolution Data

Background

Blood pressure variability (BPV) is associated with outcome after endovascular thrombectomy in acute large vessel occlusion stroke. We aimed to provide the optimal sampling frequency and BPV index for outcome prediction by using high-resolution blood pressure (BP) data.

Methods

Patient characteristics, 3-month outcome, and BP values measured intraarterially at 1 Hz for up to 24 h were extracted from 34 patients treated at a tertiary care center neurocritical care unit. Outcome was dichotomized (modified Rankin Scale 0–2, favorable, and 3–6, unfavorable) and associated with systolic BPV (as calculated by using standard deviation, coefficient of variation, averaged real variability, successive variation, number of trend changes, and a spectral approach using the power of specific BP frequencies). BP values were downsampled by either averaging or omitting all BP values within each prespecified time bin to compare the different sampling rates.

Results

Out of 34 patients (age 72 ± 12.7 years, 67.6% men), 10 (29.4%) achieved a favorable functional outcome and 24 (70.6%) had an unfavorable functional outcome at 3 months. No group differences were found in mean absolute systolic BP (SBP) (130 ± 18 mm Hg, p = 0.82) and diastolic BP (DBP) (59 ± 10 mm Hg, p = 1.00) during the monitoring time. BPV only reached predictive significance when using successive variation extracted from downsampled (averaged over 5 min) SBP data (median 4.8 mm Hg [range 3.8–7.1]) in patients with favorable versus 7.1 mmHg [range 5.5–9.7] in those with unfavorable outcome, area under the curve = 0.74 [confidence interval (CI) 0.57–0.85; p = 0.031], or the power of midrange frequencies between 1/20 and 1/5 min [area under the curve = 0.75 (CI 0.59–0.86), p = 0.020].

Conclusions

Using high-resolution BP data of 1 Hz, downsampling by averaging all BP values within 5-min intervals is essential to find relevant differences in systolic BPV, as noise can be avoided (confirmed by the significance of the power of midrange frequencies). These results demonstrate how high-resolution BP data can be processed for effective outcome prediction.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12028-022-01519-x.

Cerebral autoregulation across the menstrual cycle in eumenorrheic women

There is emerging evidence that ovarian hormones play a significant role in the lower stroke incidence observed in pre‐menopausal women compared with men. However, the role of ovarian hormones in cerebrovascular regulation remains to be elucidated. We examined the blood pressure‐cerebral blood flow relationship (cerebral autoregulation) across the menstrual cycle in eumenorrheic women (n = 12; mean ± SD: age, 31 ± 7 years). Participants completed sit‐to‐stand and Valsalva maneuvers (VM, mouth pressure of 40 mmHg for 15 s) during the early follicular (EF), late follicular (LF), and mid‐luteal (ML) menstrual cycle phases, confirmed by serum measurement of progesterone and 17β‐estradiol. Middle cerebral artery blood velocity (MCAv), arterial blood pressure and partial pressure of end‐tidal carbon dioxide were measured. Cerebral autoregulation was assessed by transfer function analysis during spontaneous blood pressure oscillations, rate of regulation (RoR) during sit‐to‐stand maneuvers, and Tieck’s autoregulatory index during VM phases II and IV (AI‐II and AI‐IV, respectively). Resting mean MCAv (MCAv_mean), blood pressure, and cerebral autoregulation were unchanged across the menstrual cycle (all p > 0.12). RoR tended to be different (EF, 0.25 ± 0.06; LF; 0.19 ± 0.04; ML, 0.18 ± 0.12 sec⁻¹; p = 0.07) and demonstrated a negative relationship with 17β‐estradiol (R² = 0.26, p = 0.02). No changes in AI‐II (EF, 1.95 ± 1.20; LF, 1.67 ± 0.77 and ML, 1.20 ± 0.55) or AI‐IV (EF, 1.35 ± 0.21; LF, 1.27 ± 0.26 and ML, 1.20 ± 0.2) were observed (p = 0.25 and 0.37, respectively). Although, a significant interaction effect (p = 0.02) was observed for the VM MCAv_mean response. These data indicate that the menstrual cycle has limited impact on cerebrovascular autoregulation, but individual differences should be considered.

Cardiovascular Autonomic Responses to Aerobic, Resistance and Combined Exercises in Resistance Hypertensive Patients

Here, we report the acute effects of aerobic (AER), resistance (RES), and combined (COM) exercises on blood pressure, central blood pressure and augmentation index, hemodynamic parameters, and autonomic modulation of resistant (RH) and nonresistant hypertensive (NON-RH) subjects. Twenty participants (10 RH and 10 NON-RH) performed three exercise sessions (i.e., AER, RES, and COM) and a control session. Hemodynamic (Finometer®, Beatscope), office blood pressure (BP), and autonomic variables (accessed through spectral analysis of the pulse-to-pulse BP signal, in the time and frequency domain-Fast Fourrier Transform) were assessed before (T0), one-hour (T1), and twenty-four (T2) hours after each experimental session. There were no changes in office BP, pulse wave behavior, and hemodynamic parameters after (T0 and T1) exercise sessions. However, AER and COM exercises significantly reduced sympathetic modulation in RH patients. It is worth mentioning that more significant changes in sympathetic modulation were observed after AER as compared to COM exercise. These findings suggest that office blood pressure, arterial stiffness, and hemodynamic parameters returned to baseline levels in the first hour and remained stable in the 24 hours after the all-exercise sessions. Notably, our findings bring new light to the effects of exercise on RH, indicating that RH patients show different autonomic responses to exercise compared to NON-RH patients. This trial is registered with trial registration number NCT02987452.

Endothelial Cullin3 Mutation Impairs Nitric Oxide-Mediated Vasodilation and Promotes Salt-Induced Hypertension

Human hypertension caused by in-frame deletion of CULLIN3 exon-9 (Cul3∆9) is driven by renal and vascular mechanisms. We bred conditionally activatable Cul3∆9 transgenic mice with tamoxifen-inducible Tie2-CRE^ERT2 mice to test the importance of endothelial Cul3. The resultant mice (E-Cul3∆9) trended towards elevated nighttime blood pressure (BP) correlated with increased nighttime activity, but displayed no difference in daytime BP or activity. Male and female E-Cul3∆9 mice together exhibited a decline in endothelial-dependent relaxation in carotid artery. Male but not female E-Cul3∆9 mice displayed severe endothelial dysfunction in cerebral basilar artery. There was no impairment in mesenteric artery and no difference in smooth muscle function, suggesting the effects of Cul3∆9 are arterial bed-specific and sex-dependent. Expression of Cul3∆9 in primary mouse aortic endothelial cells decreased endogenous Cul3 protein, phosphorylated (S1177) endothelial nitric oxide synthase (eNOS) and nitric oxide (NO) production. Protein phosphatase (PP) 2A, a known Cul3 substrate, dephosphorylates eNOS. Cul3∆9-induced impairment of eNOS activity was rescued by a selective PP2A inhibitor okadaic acid, but not by a PP1 inhibitor tautomycetin. Because NO deficiency contributes to salt-induced hypertension, we tested the salt-sensitivity of E-Cul3∆9 mice. While both male and female E-Cul3∆9 mice developed salt-induced hypertension and renal injury, the pressor effect of salt was greater in female mutants. The increased salt-sensitivity in female E-Cul3∆9 mice was associated with decreased renovascular relaxation and impaired natriuresis in response to a sodium load. Thus, CUL3 mutations in the endothelium may contribute to human hypertension in part through decreased endothelial NO bioavailability, renovascular dysfunction, and increased salt-sensitivity of BP.

Acute and Short-Term Autonomic and Hemodynamic Responses to Transcranial Direct Current Stimulation in Patients With Resistant Hypertension

Previously, we demonstrated that acute transcranial direct current stimulation (tDCS) reduced blood pressure (BP) and improved autonomic modulation in hypertensives. We hypothesized that acute and short-term tDCS intervention can promote similar benefits in resistant hypertensive patients (RHT). We assessed the impact of one (acute intervention) and ten (short-term intervention) tDCS or SHAM (20 min, each) sessions on BP, pulse interval (PI) and systolic blood pressure variabilities, humoral mechanisms associated with BP regulation, and cytokines levels. True RHT subjects (n = 13) were randomly submitted to one and ten SHAM and tDCS crossing sessions (1 week of “washout”). Hemodynamic (Finometer^®, Beatscope), office BP, and autonomic variables (accessed through spectral analysis of the pulse-to-pulse BP signal, in the time and frequency domain – Fast Fourrier Transform) were measured at baseline and after the short-term intervention. 24 h-ambulatory BP monitoring was measured after acute and short-term protocols. Acute intervention: tDCS reduced BP, cardiac output, and increase high-frequency band of PI (vagal modulation to the heart). Short-term protocol: tDCS did not change BP and cardiac output parameters. In contrast, central systolic BP (−12%), augmentation index (−31%), and pulse wave velocity (34%) were decreased by the short-term tDCS when compared to SHAM. These positive results were accompanied by a reduction in the low-frequency band (−37%) and an increase of the high-frequency band of PI (+62%) compared to SHAM. These findings collectively indicate that short-term tDCS concomitantly improves resting cardiac autonomic control and pulse wave behavior and reduces central BP in RHT patients, https://ensaiosclinicos.gov.br/rg/RBR-8n7c9p.

Integrative cerebral blood flow regulation in ischemic stroke

Optimizing cerebral perfusion is key to rescuing salvageable ischemic brain tissue. Despite being an important determinant of cerebral perfusion, there are no effective guidelines for blood pressure (BP) management in acute stroke. The control of cerebral blood flow (CBF) involves a myriad of complex pathways which are largely unaccounted for in stroke management. Due to its unique anatomy and physiology, the cerebrovascular circulation is often treated as a stand-alone system rather than an integral component of the cardiovascular system. In order to optimize the strategies for BP management in acute ischemic stroke, a critical reappraisal of the mechanisms involved in CBF control is needed. In this review, we highlight the important role of collateral circulation and re-examine the pathophysiology of CBF control, namely the determinants of cerebral perfusion pressure gradient and resistance, in the context of stroke. Finally, we summarize the state of our knowledge regarding cardiovascular and cerebrovascular interaction and explore some potential avenues for future research in ischemic stroke.

Dynamic Temporal Relationship Between Autonomic Function and Cerebrovascular Reactivity in Moderate/Severe Traumatic Brain Injury

There has been little change in morbidity and mortality in traumatic brain injury (TBI) in the last 25 years. However, literature has emerged linking impaired cerebrovascular reactivity (a surrogate of cerebral autoregulation) with poor outcomes post-injury. Thus, cerebrovascular reactivity (derived through the pressure reactivity index; PRx) is emerging as an important continuous measure. Furthermore, recent literature indicates that autonomic dysfunction may drive impaired cerebrovascular reactivity in moderate/severe TBI. Thus, to improve our understanding of this association, we assessed the physiological relationship between PRx and the autonomic variables of heart rate variability (HRV), blood pressure variability (BPV), and baroreflex sensitivity (BRS) using time-series statistical methodologies. These methodologies include vector autoregressive integrative moving average (VARIMA) impulse response function analysis, Granger causality, and hierarchical clustering. Granger causality testing displayed inconclusive results, where PRx and the autonomic variables had varying bidirectional relationships. Evaluating the temporal profile of the impulse response function plots demonstrated that the autonomic variables of BRS, ratio of low/high frequency of HRV and very low frequency HRV all had a strong relation to PRx, indicating that the sympathetic autonomic response may be more closely linked to cerebrovascular reactivity, then other variables. Finally, BRS was consistently associated with PRx, possibly demonstrating a deeper relationship to PRx than other autonomic measures. Taken together, cerebrovascular reactivity and autonomic response are interlinked, with a bidirectional impact between cerebrovascular reactivity and circulatory autonomics. However, this work is exploratory and preliminary, with further study required to extract and confirm any underlying relationships.

A G-protein-biased S1P1 agonist, SAR247799, improved LVH and diastolic function in a rat model of metabolic syndrome

Aim

Heart failure with preserved ejection fraction (HFpEF) is a major cause of death worldwide with no approved treatment. Left ventricular hypertrophy (LVH) and diastolic dysfunction represent the structural and functional components of HFpEF, respectively. Endothelial dysfunction is prevalent in HFpEF and predicts cardiovascular events. We investigated if SAR247799, a G-protein-biased sphingosine-1-phosphate receptor 1 (S1P1) agonist with endothelial-protective properties, could improve cardiac and renal functions in a rat model of metabolic syndrome LVH and diastolic function.

Methods

31- and 65-week-old obese ZSF1 (Ob-ZSF1) rats, representing adult and aged animals with LVH and diastolic dysfunction, were randomized to a chow diet containing 0.025% (w/w) of SAR247799, or control (CTRL) chow for 4 weeks. Age-matched lean ZSF1 (Le-ZSF1) rats were fed control chow. Echocardiography, telemetry, biochemical and histological analysis were performed to evaluate the effect of SAR247799.

Results

Echocardiography revealed that Ob-ZSF1 rats, in contrast to Le-ZSF1 rats, developed progressive diastolic dysfunction and cardiac hypertrophy with age. SAR247799 blunted the progression of diastolic dysfunction in adult and aged animals: in adult animals E/e’ was evaluated at 21.8 ± 1.4 for Ob-ZSF1-CTRL, 19.5 ± 1.2 for Ob-ZSF1-SAR247799 p<0.01, and 19.5 ± 2.3 for Le-ZSF1-CTRL (median ± IQR). In aged animals E/e’ was evaluated at 23.15 ± 4.45 for Ob-ZSF1-CTRL, 19.5 ± 5 for Ob-ZSF1-SAR247799 p<0.01, and 16.69 ± 1.7 for Le-ZSF1-CTRL, p<0.01 (median ± IQR). In aged animals, SAR247799 reduced cardiac hypertrophy (g/mm mean ± SEM of heart weight/tibia length 0.053 ± 0.001 for Ob-ZSF1-CTRL vs 0.046 ± 0.002 for Ob-ZSF1-SAR247799 p<0.01, Le-ZSF1-CTRL 0.035 ± 0.001) and myocardial perivascular collagen content (p<0.001), independently of any changes in microvascular density. In adult animals, SAR247799 improved endothelial function as assessed by the very low frequency bands of systolic blood pressure variability (mean ± SEM 67.8 ± 3.41 for Ob-ZSF1-CTRL 55.8 ± 4.27 or Ob-ZSF1-SAR247799, p<0.05 and 57.3 ± 1.82 Le-ZSF1-CTRL), independently of any modification of arterial blood pressure. In aged animals, SAR247799 reduced urinary protein/creatinine ratio, an index of glomerular injury, (10.3 ± 0.621 vs 8.17 ± 0.231 for Ob-ZSF1-CTRL vs Ob-ZSF1-SAR247799, respectively, p<0.05 and 0.294 ± 0.029 for Le-ZSF1-CTRL, mean ± SEM) and the fractional excretion of electrolytes. Circulating lymphocytes were not decreased by SAR247799, confirming lack of S1P1 desensitization.

Conclusions

These experimental findings suggest that S1P1 activation with SAR247799 may be considered as a new therapeutic approach for LVH and diastolic dysfunction, major components of HFpEF.

Complex sympathetic regulation in adolescent mitral valve prolapse

Mitral valve prolapse (MVP) belongs to cardiac disorders characterized by impaired closure of mitral leaflets. We studied adolescent group of patients with MVP suffering from symptomatology that cannot be explained by mitral regurgitation alone. Several studies suggested that symptoms can be explained by autonomic, in particular sympathetic-linked dysfunction. Thus, we assessed non-invasive sympathetic indices of blood pressure and heart rate variability and electrodermal activity (EDA). Fifty-three adolescents with MVP (age: 15.1+/-0.4 years) and 43 healthy age- and gender-matched adolescents (age: 14.9+/-0.4 years) were examined. Blood pressure, heart rate and EDA were continuously recorded during 6-min rest. Evaluated parameters were: low frequency band of systolic blood pressure variability, systolic, diastolic and mean blood pressure, mean RR interval, cardiac sympathetic indices: symbolic dynamics (0V%), left ventricular ejection time (LVET), pre-ejection period (PEP), and EDA. Our findings revealed significantly higher systolic, diastolic, and mean blood pressure values, shortened mean RR interval, increased 0V%, and shortened LVET in MVP patients vs. controls (p=0.028, p<0.001, p=0.002, p<0.001, p=0.050, p<0.001; respectively). Our study revealed enhanced cardiovascular sympathetic regulation in adolescent MVP patients. We suggest that evaluation of non-invasive sympathetic parameters could represent potential biomarkers for early diagnosis of cardiovascular complications associated with MVP already at adolescent age.

ACUTE TRANSCRANIAL DIRECT CURRENT STIMULATION (tDCS) IMPROVES VENTILATORY VARIABILITY AND AUTONOMIC MODULATION IN RESISTANT HYPERTENSIVE PATIENTS

Here, we assessed the impact of one session of transcranial direct current stimulation (tDCS) or SHAM (20 min, each) on ventilatory responses to cardiopulmonary exercise test, central and peripheral blood pressure (BP), and autonomic modulation in resistant hypertensive (RHT) patients. RHT subjects (n = 13) were randomly submitted to SHAM and tDCS crossing sessions (1 week of "washout"). Patients and a technician who set the tDCS/Sham room up were both blind. After brain stimulation, patients were submitted to a cardiopulmonary exercise test to evaluate ventilatory and cardiovascular response to exercise. Hemodynamic (Finometer®, Beatscope), and autonomic variables were measured at baseline (before tDCS/Sham) and after incremental exercise. RESULTS: Our study shows that tDCS condition improved heart rate recovery, VO2 peak, and vagal modulation (after cardiopulmonary exercise test); attenuated the ventilatory variability response, central and peripheral blood pressure well as sympathetic modulation (after cardiopulmonary exercise test) in comparison with SHAM. These data suggest that acute tDCS sessions prevented oscillatory ventilation behavior during the cardiopulmonary exercise test and mitigated the increase of systolic blood pressure in RHT patients. After the exercise test, tDCS promotes better vagal reentry and improved autonomic modulation, possibly reducing central blood pressure and aortic augmentation index compared to SHAM. Brazilian Registry of Clinical Trials (ReBEC): https://ensaiosclinicos.gov.br/rg/RBR-8n7c9p.

Heart Rate Variability and Cardiovascular Fitness: What We Know so Far

Fluctuation analysis in intervals between heartbeats provides important indices related to autonomic modulation of heart rate variability (HRV). These indices are considered predictors of morbidity and mortality as they are frequently altered in patients with chronic degenerative diseases, especially in those with cardiovascular and metabolic diseases. Similarly, a reduction in HRV is common with aging. In all cases, cardiovascular fitness is often reduced to below the predicted values. In turn, increases in cardiovascular fitness through regular physical exercise, especially aerobic exercise, represent an important therapeutic tool capable of promoting positive adjustments in cardiac autonomic modulation. These adjustments are characterized by reduced sympathetic modulatory influence and/or increased vagal modulatory influence on the heart, increasing the HRV. Therefore, several methodological tools have been used to assess the degree of impairment of autonomic modulation and the therapeutic effects of physical exercise. In contrast, establishment of strict protocols in experimental design is a main challenge in establishing HRV analysis as a robust parameter for evaluating cardiovascular homeostasis. Thus, this review aimed to contribute to the understanding of autonomic modulation of HRV and its relationship with cardiovascular fitness, highlighting the advances made thus far, the applicability of analysis tools, and the confounding factors observed frequently.

Integrated cardiorespiratory system model with short timescale control mechanisms

A compartmental model of the cardiorespiratory system featuring pulsatile blood flow and gas transport, as well as closed loop mechanisms of cardiorespiratory regulation is presented. Short timescale regulatory action includes baroreflex, peripheral and central chemoreflex feedback. The cardiorespiratory model is composed by compartments to describe blood flow and gas exchange in the major systemic and pulmonic regions. The control systems include formulations to afferent activity of arterial baroreceptor and peripheral and central chemoreceptors. Simulations described here include situations of hypoxia, hypercapnia, and hemorrhage. The overall responses of our simulations agree with physiological (experimental) and theoretical data. Our results suggest that the present model could be used to further understand the interplay among major regulatory mechanisms in the functioning of the cardiovascular and respiratory systems in cases of normal and abnormal physiological conditions.

Alternations in the Cardiovascular Autonomic Regulation and Growth Factors in Autism

Autism spectrum disorder (ASD) represents a serious neurodevelopmental disorder associated with autonomic nervous system dysregulation. The aim was to study complex cardiovascular autonomic regulation using heart rate variability (HRV) and systolic blood pressure variability (SBPV) linear/non-linear analysis at rest and during orthostasis, and to assess plasma levels of epidermal growth factor (EGF) and vascular endothelial growth factor (VEGF) in autistic children. Twenty-five ASD boys and 25 age and gender-matched children at the age 7-15 years were examined. After venous blood taking, continuous ECG and blood pressure biosignals were recorded at rest and during orthostasis. Evaluated parameters: RR intervals, high- and low-frequency band of HRV spectral analysis (HF-HRV, LF-HRV), symbolic dynamics parameters 0V%, 1V%, 2LV%, 2UV%, low- and high-frequency band of SBPV (LF-SBPV, HF-SBPV), systolic, diastolic, mean blood pressure, EGF, VEGF plasma levels. RR intervals were significantly shortened and the HF-HRV, LF-SBPV, HF-SBPV parameters were significantly lower at rest, the HF-HRV and LF-SBPV remained lower during orthostasis in autistic children compared to controls (p<0.05). EGF plasma levels were significantly lower in ASD compared to controls (p=0.046). No significant differences were found in remaining parameters. Our study revealed tachycardia, cardiovagal underactivity, and blunted sympathetic vasomotor regulation at rest and during orthostasis in autistic children. Additionally, complex heart rate dynamics are similar in autistic children than controls. Furthermore, EGF was reduced in autistic children without significant correlations with any autonomic parameters. We suggest that the abnormal complex cardiovascular reflex control could contribute to understanding the pathway linking autonomic features and autism.

Renal denervation does not affect hypertension or the renin-angiotensin system in a rodent model of juvenile-onset polycystic kidney disease: clinical implications

We examined the effect of total and afferent renal denervation (RDN) on hypertension and the renin-angiotensin system (RAS) in a rodent model of juvenile-onset polycystic kidney disease (PKD). Lewis Polycystic Kidney (LPK) and control rats received total, afferent or sham RDN by periaxonal application of phenol, capsaicin or normal saline, respectively, and were monitored for 4-weeks. Afferent RDN did not affect systolic blood pressure (SBP) determined by radiotelemetry in either strain (n = 19) while total RDN significantly reduced SBP in Lewis rats 4-weeks post-denervation (total vs. sham, 122 ± 1 vs. 130 ± 2 mmHg, P = 0.002, n = 25). Plasma and kidney renin content determined by radioimmunoassay were significantly lower in LPK vs. Lewis (plasma: 278.2 ± 6.7 vs. 376.5 ± 11.9 ng Ang I/ml/h; kidney: 260.1 ± 6.3 vs. 753.2 ± 37.9 ng Ang I/mg/h, P < 0.001, n = 26). These parameters were not affected by RDN. Intrarenal mRNA expression levels of renin, angiotensinogen, angiotensin-converting enzyme (ACE)2, and angiotensin II receptor type 1a were significantly lower, whereas ACE1 expression was significantly higher in the LPK vs. Lewis (all P < 0.05, n = 26). This pattern of intrarenal RAS expression was not changed by RDN. In conclusion, RDN does not affect hypertension or the RAS in the LPK model and indicates RDN might not be a suitable antihypertensive strategy for individuals with juvenile-onset PKD.

Effects of Experimental Sleep Restriction on Ambulatory and Sleep Blood Pressure in Healthy Young Adults: A Randomized Crossover Study

[Figure: see text].

The autonomic nervous system in septic shock and its role as a future therapeutic target: a narrative review

The autonomic nervous system (ANS) regulates the cardiovascular system. A growing body of experimental and clinical evidence confirms significant dysfunction of this regulation during sepsis and septic shock. Clinical guidelines do not currently include any evaluation of ANS function during the resuscitation phase of septic shock despite the fact that the severity and persistence of ANS dysfunction are correlated with worse clinical outcomes. In the critical care setting, the clinical use of ANS-related hemodynamic indices is currently limited to preliminary investigations trying to predict and anticipate imminent clinical deterioration. In this review, we discuss the evidence supporting the concept that, in septic shock, restoration of ANS-mediated control of the cardiovascular system or alleviation of the clinical consequences induced by its dysfunction (e.g., excessive tachycardia, etc.), may be an important therapeutic goal, in combination with traditional resuscitation targets. Recent studies, which have used standard and advanced monitoring methods and mathematical models to investigate the ANS-mediated mechanisms of physiological regulation, have shown the feasibility and importance of monitoring ANS hemodynamic indices at the bedside, based on the acquisition of simple signals, such as heart rate and arterial blood pressure fluctuations. During the early phase of septic shock, experimental and/or clinical studies have shown the efficacy of negative-chronotropic agents (i.e., beta-blockers or ivabradine) in controlling persistent tachycardia despite adequate resuscitation. Central α-2 agonists have been shown to prevent peripheral adrenergic receptor desensitization by reducing catecholamine exposure. Whether these new therapeutic approaches can safely improve clinical outcomes remains to be confirmed in larger clinical trials. New technological solutions are now available to non-invasively modulate ANS outflow, such as transcutaneous vagal stimulation, with initial pre-clinical studies showing promising results and paving the way for ANS modulation to be considered as a new potential therapeutic target in patients with septic shock.

Autoregulatory or Fixed Cerebral Perfusion Pressure Targets in Traumatic Brain Injury: Determining Which Is Better in an Energy Metabolic Perspective

Current guidelines in traumatic brain injury (TBI) recommend a cerebral perfusion pressure (CPP) within the fixed interval of 60-70 mm Hg. However, the autoregulatory, optimal CPP target (CPPopt) might yield better cerebral blood flow (CBF) regulation. In this study, we investigated fixed versus autoregulatory CPP targets in relation to cerebral energy metabolism and clinical outcome after TBI. Ninety-eight non-craniectomized patients with severe TBI treated in the neurointensive care unit, Uppsala University Hospital, Sweden, 2008-2018, were included. Data from cerebral microdialysis (MD), intracranial pressure (ICP), pressure autoregulation, CPP and CPPopt55-15 (a variant of CPPopt based on filtered slow waves from 15-55 sec range) were analyzed the first 10 days. The good monitoring time (GMT %) below/within/above the fixed and autoregulatory CPP targets were calculated. CPPopt55-15 was >70 mm Hg 74% of the time the first 10 days. Higher GMT (%) ΔCPPopt55-15 ± 10 mm Hg correlated with lower lactate/pyruvate ratio (LPR) on day 1 and lower cerebral glycerol on days 6-10, and predicted favorable clinical outcome. Higher GMT (%) CPP within 60-70 mm Hg correlated with lower cerebral glucose on days 2-10 and higher LPR on days 6-10, but predicted favorable clinical outcome. Higher GMT (%) CPP >70 mm Hg had the opposite associations; that is, with higher cerebral glucose and lower LPR, but unfavorable clinical outcome. Autoregulatory CPP targets may be beneficial, because patients with CPP values close to the optimal CPP had both better cerebral energy metabolism and better clinical outcome, but this needs to be evaluated in randomized trials.

Activation of the cholinergic antiinflammatory reflex by occipitoatlantal decompression and transcutaneous auricular vagus nerve stimulation

CONTEXT

The parasympathetic-mediated inflammatory reflex inhibits excessive proinflammatory cytokine production. Noninvasive techniques, including occipitoatlantal decompression (OA-D) and transcutaneous auricular vagus nerve stimulation (taVNS), have been demonstrated to increase parasympathetic tone.

OBJECTIVES

To test the hypothesis that OA-D and taVNS increase parasympathetic nervous system activity and inhibit proinflammatory cytokine mobilization and/or production.

METHODS

Healthy adult participants were randomized to receive OA-D (5 min of OA-D followed by 10 min of rest; n=8), taVNS (15 min; n=9), or no intervention (15 min, time control; n=10) on three consecutive days. Before and after these interventions, saliva samples were collected for determination of the cytokines interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-8 (IL-8), and tumor necrosis factor α (TNF-α). Arterial blood pressure and the electrocardiogram were recorded for a 30-min baseline, throughout the intervention, and during a 30-min recovery period to derive heart rate and blood pressure variability markers as indices of vagal and sympathetic control.

RESULTS

OA-D and taVNS increased root mean square of successive RR interval differences (RMSSD) and high frequency heart rate variability, which are established markers for parasympathetic modulation of cardiac function. In all three groups, the experimental protocol was associated with a significant increase in salivary cytokine concentrations. However, the increase in IL-1β was significantly less in the taVNS group (+66 ± 13 pg/mL; p<0.05) than in the time control group (+142 ± 24 pg/mL). A similar trend was observed in the taVNS group for TNF-α (+1.7 ± 0.3 pg/mL vs. 4.1 ± 1.3 pg/mL; p<0.10). In the OA-D group baseline IL-6, IL-8, and TNF-α levels on the third study day were significantly lower than on the first study day (IL-6: 2.3 ± 0.4 vs. 3.2 ± 0.6 pg/mL, p<0.05; IL-8: 190 ± 61 vs. 483 ± 125 pg/mL, p <0.05; TNF-α: 1.2 ± 0.3 vs. 2.3 ± 0.4 pg/mL, p<0.05). OA-D decreased mean blood pressure from the first (100 ± 8 mmHg) to the second (92 ± 6 mmHg; p<0.05) and third (93 ± 8 mmHg; p<0.05) study days and reduced low frequency spectral power of systolic blood pressure variability (19 ± 3 mmHg² after OA-D vs. 28 ± 5 mmHg² before OA-D; p<0.05), a marker of sympathetic modulation of vascular tone. OA-D also increased baroreceptor-heart rate reflex sensitivity from the first (13.7 ± 3.0 ms/mmHg) to the second (18.4 ± 4.3 ms/mmHg; p<0.05) and third (16.9 ± 4.2 ms/mmHg; p<0.05) study days.

CONCLUSIONS

Both OA-D and taVNS elicited antiinflammatory responses that were associated with increases in heart rate variability-derived markers for parasympathetic function. These findings suggest that OA-D and taVNS activate the parasympathetic antiinflammatory reflex. Furthermore, an antihypertensive effect was observed with OA-D that may be mediated by reduced sympathetic modulation of vascular tone and/or increased baroreceptor reflex sensitivity.

Nebivolol is more effective than atenolol for blood pressure variability attenuation and target organ damage prevention in L-NAME hypertensive rats

β-Adrenergic blockers are no longer recommended as first-line therapy due to the reduced cardioprotection of traditional β-blockers compared with other antihypertensive drugs. It is unknown whether third-generation β-blockers share the limitations of traditional β-blockers. The aim of the present study was to compare the effects of nebivolol or atenolol on central and peripheral systolic blood pressure (SBP) and its variability and target organ damage (TOD) in N-nitro-L-arginine methyl ester (L-NAME) hypertensive rats. Male Wistar rats were treated with L-NAME for 8 weeks together with oral administration of nebivolol 30 mg/kg (n = 8), atenolol 90 mg/kg (n = 8), or vehicle (n = 8). The control group was composed of vehicle-treated Wistar rats. SBP and its variability, as well as echocardiographic parameters, were assessed during the last 2 weeks of treatment. Tissue levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and transforming growth factor β (TGF-β), and histopathological parameters were evaluated in the left ventricle and aorta. Nebivolol had a greater ability than atenolol to decrease central SBP and mid-term and short-term blood pressure variability (BPV) in L-NAME rats. Echocardiographic analysis showed that nebivolol was more effective than atenolol on E/A wave ratio normalization. Compared with atenolol treatment, nebivolol had a greater protective effect on different TOD markers, inducing a decrease in collagen deposition and a reduction in the proinflammatory cytokines IL-6 and TNF-α in the left ventricle and aorta. Our findings suggest that the adverse hemodynamic profile and the reduced cardiovascular protection reported with traditional β-blockers must not be carried forward to third-generation β-blockers.

Assessment of Outliers and Detection of Artifactual Network Segments Using Univariate and Multivariate Dispersion Entropy on Physiological Signals

Network physiology has emerged as a promising paradigm for the extraction of clinically relevant information from physiological signals by moving from univariate to multivariate analysis, allowing for the inspection of interdependencies between organ systems. However, for its successful implementation, the disruptive effects of artifactual outliers, which are a common occurrence in physiological recordings, have to be studied, quantified, and addressed. Within the scope of this study, we utilize Dispersion Entropy (DisEn) to initially quantify the capacity of outlier samples to disrupt the values of univariate and multivariate features extracted with DisEn from physiological network segments consisting of synchronised, electroencephalogram, nasal respiratory, blood pressure, and electrocardiogram signals. The DisEn algorithm is selected due to its efficient computation and good performance in the detection of changes in signals for both univariate and multivariate time-series. The extracted features are then utilised for the training and testing of a logistic regression classifier in univariate and multivariate configurations in an effort to partially automate the detection of artifactual network segments. Our results indicate that outlier samples cause significant disruption in the values of extracted features with multivariate features displaying a certain level of robustness based on the number of signals formulating the network segments from which they are extracted. Furthermore, the deployed classifiers achieve noteworthy performance, where the percentage of correct network segment classification surpasses 95% in a number of experimental setups, with the effectiveness of each configuration being affected by the signal in which outliers are located. Finally, due to the increase in the number of features extracted within the framework of network physiology and the observed impact of artifactual samples in the accuracy of their values, the implementation of algorithmic steps capable of effective feature selection is highlighted as an important area for future research.

Study of heart rate recovery and cardiovascular autonomic modulation in healthy participants after submaximal exercise

Heart rate variability (HRV), blood pressure variability (BPV), and baroreflex sensitivity (BRS) provide important information on cardiovascular autonomic control. However, little is known about the reorganization of HRV, BPV, and BRS after aerobic exercise. While there is a positive relationship between heart rate (HR) recovery rate and cardiorespiratory fitness, it is unclear whether there is a relationship between cardiorespiratory fitness and reorganization of cardiovascular autonomic modulation during recovery. Thus, this study aimed to investigate whether cardiorespiratory fitness influences the cardiovascular autonomic modulation recovery, after a cardiopulmonary exercise test. Sixty men were assigned into groups according to their cardiorespiratory fitness: low cardiorespiratory fitness (LCF = VO2: 22–38 mL kg⁻¹ min⁻¹), moderate (MCF = VO2: 38–48 mL kg⁻¹ min⁻¹), and high (HCF = VO2 > 48 mL kg⁻¹ min⁻¹). HRV (linear and non-linear analysis) and BPV (spectral analysis), and BRS (sequence method) were performed before and after a cardiopulmonary exercise test. The groups with higher cardiorespiratory fitness had lower baseline HR values and HR recovery time after the cardiopulmonary exercise test. On comparing rest and recovery periods, the spectral analysis of HRV showed a decrease in low-frequency (LF) oscillations in absolute units and high frequency (HF) in absolute and normalized units. It also showed increases in LF oscillations of blood pressure. Nonlinear analysis showed a reduction in approximate entropy (ApEn) and in Poincare Plot parameters (SD1 and SD2), accompanied by increases in detrended fluctuation analysis (DFA) parameters α1 and α2. However, we did not find differences in cardiovascular autonomic modulation parameters and BRS in relation to cardiorespiratory fitness neither before nor after the cardiopulmonary test. We concluded that cardiorespiratory fitness does not affect cardiovascular autonomic modulations after cardiopulmonary exercise test, unlike HR recovery.

Beat-to-beat blood pressure variability: an early predictor of disease and cardiovascular risk

Blood pressure (BP) varies on the long, short and very-short term. Owing to the hidden physiological and pathological information present in BP time-series, increasing interest has been given to the study of continuous, beat-to-beat BP variability (BPV) using invasive and noninvasive methods. Different linear and nonlinear parameters of variability are employed in the characterization of BP signals in health and disease. Although linear parameters of beat-to-beat BPV are mainly measures of dispersion, such as standard deviation (SD), nonlinear parameters of BPV quantify the degree of complexity/irregularity- using measures of entropy or self-similarity/correlation. In this review, we summarize the value of linear and nonlinear parameters in reflecting different information about the pathophysiology of changes in beat-to-beat BPV independent of or superior to mean BP. We then provide a comparison of the relative power of linear and nonlinear parameters of beat-to-beat BPV in detecting early and subtle differences in various states. The practical advantage and utility of beat-to-beat BPV monitoring support its incorporation into routine clinical practices.

Failure to vasodilate in response to salt loading blunts renal blood flow and causes salt-sensitive hypertension

AIMS

Salt-sensitive (SS) hypertension is accompanied by impaired vasodilation in the systemic and renal circulation. However, the causal relationship between vascular dysfunction and salt-induced hypertension remains controversial. We sought to determine whether primary vascular dysfunction, characterized by a failure to vasodilate during salt loading, plays a causal role in the pathogenesis of SS hypertension.

METHODS AND RESULTS

Mice selectively expressing a peroxisome proliferator-activated receptor γ dominant-negative mutation in vascular smooth muscle (S-P467L) exhibited progressive SS hypertension during a 4 week high salt diet (HSD). This was associated with severely impaired vasodilation in systemic and renal vessels. Salt-induced impairment of vasodilation occurred as early as 3 days after HSD, which preceded the onset of SS hypertension. Notably, the overt salt-induced hypertension in S-P467L mice was not driven by higher cardiac output, implying elevations in peripheral vascular resistance. In keeping with this, HSD-fed S-P467L mice exhibited decreased smooth muscle responsiveness to nitric oxide (NO) in systemic vessels. HSD-fed S-P467L mice also exhibited elevated albuminuria and a blunted increase in urinary NO metabolites which was associated with blunted renal blood flow and increased sodium retention mediated by a lack of HSD-induced suppression of NKCC2. Blocking NKCC2 function prevented the salt-induced increase in blood pressure in S-P467L mice.

CONCLUSION

We conclude that failure to vasodilate in response to salt loading causes SS hypertension by restricting renal perfusion and reducing renal NO through a mechanism involving NKCC2 in a mouse model of vascular peroxisome proliferator-activated receptor γ impairment.

Blood Pressure Variability and Baroreflex Sensitivity in Premature Newborns-An Effect of Postconceptional and Gestational Age

Introduction: Cardiovascular system is the vitally important system in the dynamical adaptation process of the newborns to the extrauterine environment. To reliably detect immaturity in the given organ system, it is crucial to study the development of the organ functions in relation to maturation process. Objectives: The objective was to determine the changes in the spontaneous short-term blood pressure variability (BPV) and baroreflex sensitivity (BRS) reflecting various aspects of cardiovascular control during the process of maturation in preterm babies and to separate effects of gestational age and postnatal age. Methods: Thirty-three prematurely born infants without any signs of cardio-respiratory disorders (gestational age: 31.8, range: 27-36 weeks; birth weight: 1,704, range: 820-2,730 grams) were enrolled. Continuous peripheral blood pressure signal was obtained by non-invasive volume-clamp photoplethysmography method during supine rest. The recordings of 250 continuous beat-to-beat blood pressure values were processed by spectral analysis of BPV (assessed measures: total power, low frequency and high frequency powers of systolic BPV) and BRS calculation. For each infant we also assessed systolic, diastolic and mean blood pressures, heart rate and respiratory rate. Results: With the postconceptional age, BPV measures decreased (for total power: Spearman correlation coefficient r_s = -0.345, P = 0.049; for low frequency power: r_s = -0.365, P = 0.037; for high frequency power r_s = -0.349; P = 0.046); and BRS increased significantly (r_s = 0.448, P = 0.009). The further analysis demonstrated that these effects were more attributable to gestational age than to postnatal age. BRS correlated negatively with BPV magnitude (r_s = -0.479 to -0.592, P = 0.001-0.005). Mean blood pressure and diastolic blood pressure increased during maturation (r_s = 0.517 and 0.537, P = 0.002 and 0.001, respectively) while heart rate and respiratory rate decreased (r_s = -0.366 and -0.516, P = 0.036 and 0.002, respectively). Conclusion: We conclude that maturation process is accompanied by an increased involvement of baroreflex buffering of spontaneous short-term blood pressure oscillations. Gestational age plays a dominant role not only in BPV changes but also in BRS, mean blood pressure, diastolic blood pressure and heart rate changes.

Effects of maternal protein restriction on central and peripheral renin-angiotensin systems in male rat offspring

AIMS

We investigated the involvement of the renin angiotensin system (RAS) on the cardiorespiratory control in rats from dams fed with a low-protein diet.

MAIN METHODS

Male offspring were obtained from dams fed a normoprotein diet (NP, 17% casein) and low-protein diet (LP, 8% casein) during pregnancy and lactation. Direct measurements of arterial pressure (AP), heart rate (HR) and respiratory frequency (RF) were recorded in awake 90-day-old at resting and after losartan potassium through either intracerebroventricular (ICV) microinjections or intravenous (IV) administration. Cardiovascular variability was evaluated by spectral analysis. Peripheral chemoreflex sensitivity was assessed through the potassium cyanide (KCN; 40 μg/0.1 ml/rat, IV). Gene expression was evaluated by qPCR, and MAPK (Mitogen Activated Protein Kinase) expression was evaluated by western blot.

KEY FINDINGS

The LP offspring had higher mean AP (MAP) and RF than NP offspring. In the spectral analysis, the LP rats also showed higher low frequency of systolic AP (NP: 2.7 ± 0.3 vs. LP: 5.0 ± 1.0 mmHg). After ICV losartan, MAP and RF in LP rats remained higher than those in NP rats, but without changes in HR. The peripheral chemoreflex was similar between the groups. LP group had lower gene expression of Rac1 (Ras-related C3 botulinum toxin substrate 1) (NP: 1.13 ± 0.06 vs. LP: 0.88 ± 0.08). Peripherally, LP rats had larger delta of MAP after IV losartan (NP: -9.8 ± 2 vs. LP: -23 ± 6 mmHg), without changes in HR and RF.

SIGNIFICANCE

In rats, the RAS participates peripherally, but not centrally, in the maintenance of arterial hypertension in male offspring induced by maternal protein restriction.

Role of Neuroendocrine, Immune, and Autonomic Nervous System in Anorexia Nervosa-Linked Cardiovascular Diseases

Anorexia nervosa represents a severe mental disorder associated with food avoidance and malnutrition. In patients suffering from anorexia nervosa, cardiovascular complications are the main reason leading to morbidity and mortality. However, the origin and pathological mechanisms leading to higher cardiovascular risk in anorexia nervosa are still unclear. In this aspect, the issue of exact pathological mechanisms as well as sensitive biomarkers for detection of anorexia nervosa-linked cardiovascular risk are discussed. Therefore, this review synthesised recent evidence of dysfunction in multiple neuroendocrine axes and alterations in the immune system that may represent anorexia nervosa-linked pathological mechanisms contributing to complex cardiovascular dysregulation. Further, this review is focused on identification of non-invasive biomarkers for the assessment of increased cardiovascular risk in anorexia nervosa that can be linked to a clinical application. Complex non-invasive assessment of cardiovascular autonomic regulation—cardiac vagal control (heart rate variability), sympathetic vascular activity (blood pressure variability), and cardiovascular reflex control (baroreflex sensitivity)—could represent a promising tool for early diagnosis, personalized therapy, and monitoring of therapeutic interventions in anorexia nervosa particularly at a vulnerable adolescent age.

Beat-to-Beat Blood Pressure Variability in the First Trimester Is Associated With the Development of Preeclampsia in a Prospective Cohort: Relation With Aortic Stiffness

Women with preeclampsia, a hypertensive disorder of pregnancy, exhibit greater beat-to-beat blood pressure variability (BPV) in the third trimester after clinical onset of the disorder. However, it remains unknown whether elevated BPV precedes the development of preeclampsia. A prospective study cohort of 139 women (age 30.2±4.0 years) were enrolled in early pregnancy (<14 weeks gestation). BPV was quantified by time domain analyses of 10-minute continuous beat-to-beat blood pressure recordings via finger photoplethysmography in the first, second, and third trimesters. Aortic stiffness (carotid-femoral pulse wave velocity) and spontaneous cardiovagal baroreflex sensitivity were also measured each trimester. Eighteen women (13%) developed preeclampsia. Systolic BPV was higher in all trimesters among women who developed versus did not develop preeclampsia (first: 4.8±1.3 versus 3.7±1.2, P=0.001; second: 5.1±1.8 versus 3.8±1.1, P=0.02; third: 5.2±0.8 versus 4.0±1.1 mm Hg, P=0.002). Elevated first trimester systolic BPV was associated with preeclampsia (odds ratio, 1.94 [95% CI, 1.27-2.99]), even after adjusting for risk factors (age, body mass index, systolic blood pressure, history of preeclampsia, and diabetes mellitus) and was a significant predictor of preeclampsia (area under the receiver operator characteristic curve=0.75±0.07; P=0.002). Carotid-femoral pulse wave velocity was elevated in the first trimester among women who developed preeclampsia (5.9±0.8 versus 5.2±0.8 m/s; P=0.002) and was associated with BPV after adjustment for mean blood pressure (r=0.26; P=0.005). First trimester baroreflex sensitivity did not differ between groups (P=0.23) and was not related to BPV (P=0.36). Elevated systolic BPV is independently associated with the development of preeclampsia as early as the first trimester, possibly mediated in part by higher aortic stiffness.

Dietary nitrate reduces blood pressure and cerebral artery velocity fluctuations and improves cerebral autoregulation in transient ischemic attack patients

We found dietary nitrate supplementation reduced blood pressure and brain blood flow fluctuations and improved the relationship between blood pressure and brain blood flow in transient ischemic attack patients. Meanwhile, dietary nitrate had no effects on the brain blood vessels’ response to CO2. We attribute the improved brain blood flow stability to the improved myogenic control of blood pressure with dietary nitrate. Our findings indicate that dietary nitrate could be an effective strategy for stabilizing blood pressure and brain blood flow following transient ischemic attack.

Blood Pressure Variability and Optimal Cerebral Perfusion Pressure-New Therapeutic Targets in Traumatic Brain Injury

BACKGROUND

Optimal cerebral perfusion pressure (CPPopt) is an autoregulatory-oriented target in the neurointensive care (NIC) of patients with traumatic brain injury (TBI), and deviation from CPPopt is associated with poor outcome. We recently found that blood pressure variability (BPV) is associated with deviation from CPPopt.

OBJECTIVE

To evaluate BPV and other variables related to deviation from CPPopt and to evaluate challenges and strategies for autoregulatory-oriented treatment in TBI.

METHODS

Data including arterial blood pressure and intracranial pressure (ICP) from 362 TBI patients treated at the NIC unit, Uppsala University Hospital, Sweden, between 2008 and 2016, were retrospectively analyzed day 2 to 5.

RESULTS

Higher BPV was a strong predictor of both CPP deviation below and above CPPopt after multiple regression analyses. There was no other explanatory variable for CPP deviation above CPPopt, whereas also higher ICP and worse autoregulation (higher pressure reactivity index) were associated with CPP deviation below CPPopt. A higher BPV was, in turn, explained by older age, lower ICP, higher mean arterial blood pressure, and higher slow arterial blood pressure amplitude (0.018-0.067 Hz).

CONCLUSION

BPV was strongly associated with deviation from CPPopt. High age is a risk factor for high BPV and hence CPP insults. Our treatment protocol is focused on avoiding CPP below 60 mm Hg. It is possible that a more restrictive upper level could generate more stable blood pressure and less deviation from CPPopt.

Vascular Decoupling in Septic Shock: The Combined Role of Autonomic Nervous System, Arterial Stiffness, and Peripheral Vascular Tone

BACKGROUND

Acute inflammation and sepsis are known to induce changes in vascular properties, leading to increased arterial stiffness; at the same time, the autonomic nervous system (ANS) also affects vascular properties by modulating the arterial smooth muscle tone, and it is widely reported that sepsis and septic shock severely impair ANS activity. Currently, clinical guidelines are mainly concerned to resuscitate septic shock patients from hypotension, hypovolemia, and hypoperfusion; however, if the current resuscitation maneuvers have a beneficial effect also on vascular properties and autonomic functionality is still unclear. The objective of this work is to assess the effects of standard resuscitation at vascular level and to verify if there is any association between alterations in vascular properties and ANS activity.

METHODS

Six pigs underwent a protocol of polymicrobial septic shock and resuscitation (fluids and noradrenaline). The arterial blood pressure (ABP) waveform was recorded in the central aorta and in the peripheral radial and femoral artery. The characteristic arterial time constant was computed at the three arterial sites based on the two-element Windkessel model, to characterize the overall arterial vascular tree. Moreover, independent estimates of total arterial compliance (AC) and total peripheral resistance (TPR) were performed. Baroreflex sensitivity (BRS), low frequency (LF, 0.04-0.15 Hz) spectral power of diastolic blood pressure, and indices of heart rate variability (HRV) were computed to assess ANS functionality.

RESULTS

Septic shock induced a severe vascular disarray, decoupling the usual pressure wave propagation from central to peripheral sites; this phenomenon appeared as an inversion of the physiological pulse pressure (PP) amplification, with a higher PP in the central aorta than in the peripheral arteries. The time constant was decreased, together with AC and TPR. ANS dysfunction was described by a reduced BRS, decreased LF power, and suppressed HRV. This compromised condition was not resolved by administration of fluids and noradrenaline. Thus, a persistent vascular and autonomic dysfunction were reported also in the resuscitated animals, and they were found to be significantly correlated.

CONCLUSION

Measures of vascular function and ANS activity could add information to standard hemodynamic and clinical markers, and the current resuscitation strategies could benefit from the adjunction of these additional functional indices.

Alternative continuous intracranial pressure-derived cerebrovascular reactivity metrics in traumatic brain injury: a scoping overview

BACKGROUND

Pressure reactivity index (PRx) has emerged as a means to continuously monitor cerebrovascular reactivity in traumatic brain injury (TBI). However, other intracranial pressure (ICP)-based continuous metrics exist, and may have advantages over PRx. The goal of this study was to perform a scoping overview of the literature on non-PRx ICP-based continuous cerebrovascular reactivity metrics in adult TBI.

METHODS

We searched MEDLINE, BIOSIS, EMBASE, Global Health, SCOPUS, and Cochrane Library from inception to December 2019. Using a two-stage filtering of title/abstract, and then full manuscript, we identified pertinent articles. Data was abstracted to tables and each technique summarized, including pulse amplitude index (PAx), correlation between pulse amplitude of ICP and cerebral perfusion pressure (RAC), PRx_55-15, and low-resolution metrics LAx and L-PRx.

RESULTS

A total of 23 articles met the inclusion criteria, with the vast majority being retrospective in nature and based out of European centers. Sixteen articles focused on high-resolution metrics PAx, RAC, and PRx_55-15, with 6 articles focusing on LAx and L-PRx. PAx may have a role in low ICP situations, where it appears to perform superior to PRx. RAC displays similar behavior to PRx, with a trend to stronger associations with favorable/unfavorable outcome at 6 months, and stronger parabolic relationship with CPP. PRx_55-15 provides a focused assessment on the vasogenic frequency range associated with cerebral autoregulation, with preliminary data supporting a strong association with outcome in TBI. LAx and L-PRx display varying associations with 6-month outcome in TBI, depending on the window length of calculation, with shorter windows demonstrating stronger correlations with classical PRx.

CONCLUSIONS

Non-PRx continuous ICP-based cerebrovascular reactivity metrics can be split into high-resolution and low-resolution measures. High-resolution indices include PAx, RAC, and PRx_55-15, while low-resolution indices include L-PRx and LAx. The true role for these metrics beyond classic PRx remains unclear. Each displays situations where it may prove superior over PRx, given limitations with this currently widely accepted measure. Much future investigation into each of these alternative metrics is required prior to adoption into the clinical monitoring armamentarium in adult TBI.

Pharmacological Suppression of Endogenous Glucocorticoid Synthesis Attenuated Blood Pressure and Heart Rate Response to Acute Restraint in Wistar Rats

Glucocorticoids (GCS) are known to modulate cardiovascular response during stress conditions. The present study was aimed to test the hypothesis that permissive and/or stimulating effect of GCs is essential for the maintenance of peripheral vascular resistance and for the adequate response of cardiovascular system to stressor exposure. The effects of acute pharmacological adrenalectomy (PhADX) on humoral and cardiovascular parameters were studied in adult Wistar rats under the basal conditions and during the acute restraint stress. Acute PhADX was performed by the administration of metyrapone and aminoglutethimide (100 mg/kg s.c. of each drug) resulting in a suppression of endogenous glucocorticoid synthesis. Blood pressure (BP), heart rate (HR) and core body temperature were measured using radiotelemetry. BP responses to administration of vasoactive agents were determined in pentobarbital-anesthetized animals. PhADX considerably attenuated stress-induced increase of BP, HR and core body temperature. PhADX did not abolish BP and HR lowering effects of ganglionic blocker pentolinium indicating preserved sympathetic function in PhADX rats. BP response to exogenous norepinephrine administration was attenuated in PhADX rats, suggesting reduced sensitivity of cardiovascular system. Suppression of corticosterone synthesis by PhADX increased basal plasma levels of ACTH, aldosterone and plasma renin activity in unstressed animals but there was no further increase of these hormones following stressor exposure. In conclusion, PhADX attenuated stress-induced rise of blood pressure, heart rate and core body temperature indicating an important permissive and/or stimulating role of glucocorticoids in the maintenance of the adequate response of cardiovascular system and thermoregulation to several stimuli including acute exposure to stressor.

An Experimental Investigation of White Matter Venous Hemodynamics: Basic Physiology and Disruption in Neuroinflammatory Disease

The white matter is highly vascularised by the cerebral venous system. In this paper, we describe a unique blood oxygen-level dependent (BOLD) signal within the white matter using functional MRI and spatial independent components analysis. The signal is characterized by a narrow peak frequency band between 0.05 and 0.1 Hz. Hypercapnia, induced transient increases in white matter venous BOLD that disrupted the oscillation indicative of a vasocontractile mechanism. Comparison of the white matter venous BOLD oscillations between 14 healthy subjects and 18 people with perivenular inflammation due to multiple sclerosis (MS), revealed loss of power in the white matter venous BOLD signal in the peak frequency band (patients = 6.70 ± 0.94 dB/Hz vs. controls = 7.64 ± 0.71 dB/Hz; p = 0.006). In MS, lower power was associated with greater levels of neuroinflammatory activity (R = −0.64, p = 0.006). Using a signal modeling technique, we assessed the anatomical distribution of white matter venous BOLD signal abnormalities and detected reduced power in the periventricular white matter, a region of known venous damage in MS. These results demonstrate a novel link between neuroinflammation and vascular physiological dysfunction in the cerebral white matter, and could indicate enduring loss of vascular compliance associated with imperfect repair of blood-brain barrier damage after resolution of acute neuroinflammation.

Phase Coupling Between Baroreflex Oscillations of Blood Pressure and Heart Rate Changes in 21-Day Dry Immersion

Introduction

Dry immersion (DI) is a ground-based experimental model which reproduces the effects of microgravity on the cardiovascular system and, therefore, can be used to study the mechanisms of post-flight orthostatic intolerance in cosmonauts. However, the effects of long-duration DI on cardiovascular system have not been studied yet. The aim of this work was to study the effects of 21-day DI on systemic hemodynamics and its baroreflex control at rest and during head-up tilt test (HUTT).

Methods

Ten healthy young men were exposed to DI for 21 days. The day before, on the 7th, 14th, and 19th day of DI, as well as on the 1st and 5th days of recovery they were subjected to HUTT: 15 min in supine position and then 15 min of orthostasis (60°). ECG, arterial pressure, stroke volume and respiration rate were continuously recorded during the test. Phase synchronization index (PSI) of beat-to-beat mean arterial pressure (MAP) and heart rate (HR) in the frequency band of baroreflex waves (∼0.1 Hz) was used as a quantitative measure of baroreflex activity.

Results

During DI, strong tachycardia and the reduction of stroke volume were observed both in supine position and during HUTT, these indicators did not recover on post-immersion day 5. In contrast, systolic arterial pressure and MAP decreased during HUTT on 14th day of DI, but then restored to pre-immersion values. Before DI and on day 5 of recovery, a transition from supine position to orthostasis was accompanied by an increase in PSI at the baroreflex frequency. However, PSI did not change in HUTT performed during DI and on post-immersion day 1. The amplitude of MAP oscillations at this frequency were increased by HUTT at all time points, while an increase of respective HR oscillations was absent during DI.

Conclusion

21-day DI drastically changed the hemodynamic response to HUTT, while its effect on blood pressure was reduced between days 14 and 19, which speaks in favor of the adaptation to the conditions of DI. The lack of increase in phase synchronization of baroreflex MAP and HR oscillations during HUTT indicates disorders of baroreflex cardiac control during DI.

Stroke Outcome Prediction by Blood Pressure Variability, Heart Rate Variability, and Baroreflex Sensitivity

Background and Purpose- Poststroke autonomic dysfunction portended an unfavorable prognosis. We investigated whether blood pressure variability (BPV), heart rate variability, and baroreflex sensitivity might predict stroke functional outcome. Methods- We calculated BPV, heart rate variability, baroreflex slope, and baroreflex effectiveness index from a 5-minute beat-to-beat blood pressure and heart rate monitoring within 7 days from the stroke onset. We compared the parameters between patients with a good outcome (modified Rankin Scale score, 0-2) and those with a poor outcome. Results- Among 142 patients (mean age, 63.9±10.2 years; 88.0% men), functional outcome was good in 112 (78.9%) and poor in 30 (21.1%). There were significant differences in admission National Institutes of Health Stroke Scale, prior stroke, high-frequency systolic BPV, low/high-frequency ratio of BPV, baroreflex sensitivity-up, and baroreflex sensitivity-total between the 2 groups (all P<0.05). In multivariate analysis, National Institutes of Health Stroke Scale (OR, 1.672 [95% CI, 1.316-2.125]; P<0.001), low/high-frequency ratio of systolic BPV (OR, 0.493 [95% CI, 0.250-0.973]; P=0.041), and baroreflex effectiveness index-down (OR, 0.958 [95% CI, 0.924-0.992]; P=0.017) independently predicted a poor functional outcome. Conclusions- A decreased low/high-frequency ratio of systolic BPV and impaired baroreflex sensitivity predicted an unfavorable stroke outcome, in addition to the established prognostic factor such as the National Institutes of Health Stroke Scale.

Effect of polycystic ovary syndrome on cardiac autonomic function at a late fertile age: a prospective Northern Finland Birth Cohort 1966 study

OBJECTIVES

Previous studies of women in their 20s and 30s have reported impaired autonomic function in women with polycystic ovary syndrome (PCOS). We aimed to study, for the first time, whether PCOS is associated with impaired cardiac autonomic function independent of metabolic and hormonal status in their late reproductive years.

DESIGN

A prospective Northern Finland Birth Cohort 1966 (NFBC1966) study including 5889 women born in 1966 and followed through the age of 46. At that age, n=3706/5123 women (72%) answered the postal questionnaires and n=3280/5123 women (64%) participated in the clinical examination.

SETTING

General community.

PARTICIPANTS

The sample included women presenting both irregular menses (oligomenorrhoea or amenorrhoea) and hirsutism at age 31 (n=125) or with formally diagnosed PCOS by age 46 (n=181) and women without PCOS symptoms or diagnosis (n=1577).

PRIMARY AND SECONDARY OUTCOME MEASURES

Heart rate variability parameters: the root mean square of successive R-R differences (rMSSD), spectral power densities (LF: low frequency and HF: high frequency) and baroreflex sensitivity (BRS).

RESULTS

We found that parasympathetic activity (assessed by rMSSD: 19.5 (12.4; 31.9) vs 24.3 (16.1; 34.8) ms, p=0.004 and HF: 172 (75; 399) vs 261 (112; 565) ms², p=0.002) and BRS (6.13±3.12 vs 6.99±3.52 ms/mm Hg, p=0.036) were lower in women with PCOS compared with the controls. However, in the multivariate regression analysis, PCOS, body mass index and the free androgen index did not significantly associate with rMSSD, whereas blood pressure, insulin resistance and triglycerides did.

CONCLUSIONS

We report here for the first time that late reproductive-aged women with PCOS display impaired cardiac autonomic function manifested as decreased vagal activity. Metabolic status, rather than hyperandrogenaemia and PCOS per se, was the strongest contributing factor. Given the link between cardiac morbidity and impaired autonomic function, the findings underline the importance of screening and treating metabolic abnormalities early on in women with PCOS.