Autonomic Cardiovascular Control Research Articles

Cardiovascular Autonomic Regulation, ETCO2 and the Heart Rate Response to the Tilt Table Test in Patients with Orthostatic Intolerance.

Chronic orthostatic intolerance (COI) is defined by changes in heart rate (HR), blood pressure (BP), respiration, symptoms of cerebral hypoperfusion and sympathetic overactivation. Postural tachycardia syndrome (POTS) is the most common form of COI in young adults and is defined by an orthostatic increase in heart rate (HR) of ≥ 30bpm in the absence of orthostatic hypotension. However, some patients referred for evaluation of COI symptoms do not meet the orthostatic HR response criterion of POTS despite debilitating symptoms. Such patients are ill defined, posing diagnostic and therapeutic challenges. This study explored the relationship among cardiovascular autonomic control, the orthostatic HR response, EtCO2 and the severity of orthostatic symptoms and fatigue in patients referred for evaluation of COI. Patients (N = 108) performed standardized testing protocol of the Autonomic Reflex Screen and completed the Composite Autonomic Symptom Score (COMPASS-31) and the Fatigue Severity Scale (FSS). Greater severity of COI was associated with younger age, larger phase IV amplitude in the Valsalva maneuver and lower adrenal baroreflex sensitivity. Greater fatigue severity was associated with a larger reduction in ETCO2 during 10min of head-up tilt (HUT) and reduced low-frequency (LF) power of heart rate variability. This study suggests that hemodynamic changes associated with the baroreflex response and changes in EtCO2 show a stronger association with the severity of orthostatic symptoms and fatigue than the overall orthostatic HR response in patients with COI.

Intracranial compliance in type 2 diabetes mellitus and its relationship with the cardiovascular autonomic nervous control.

The intracranial compliance in type 2 diabetes mellitus (T2DM) patients and the association with cardiovascular autonomic control have not been fully elucidated. The aim of this study was to assess intracranial compliance using the noninvasive intracranial pressure (niICP) and the monitoring of waveform peaks (P1, P2, and P3) and the relationship with cardiovascular autonomic control in T2DM patients. Thirty-two men aged 40-60 years without cardiovascular autonomic neuropathy (CAN) were studied: T2DMG (n=16) and control group CG (n=16). The niICP was evaluated by a noninvasive extracranial sensor placed on the scalp. Cardiovascular autonomic control was evaluated by indices of the baroreflex sensitivity (BRS), from temporal series of R-R intervals of electrocardiogram and systolic arterial pressure, during supine and orthostatic positions. The participants remained in the supine position for 15 min and then 15 min more in orthostatism. T2DMG presented a decrease of the P2/P1 ratio during the orthostatic position (P<0.001). There was a negative moderate correlation between the P2 peak with cardiovascular coupling (K2 HP-SAPLF) in supine (r=-0.612, P=0.011) and orthostatic (r=-0.568, P=0.020) positions in T2DMG. We concluded that T2DM patients without CAN and cardiovascular complications presented intracranial compliance similar to healthy subjects. Despite preserved intracranial adjustments, T2DM patients had a response of greater magnitude in orthostatism. In addition, the decoupling between the heart period and blood pressure signal oscillations in low frequency appeared to be related to the worsening of intracranial compliance due to the increased P2 peak.

Role of aerobic physical training on cardiac autonomic and morphophysiological dysfunction in hypertensive rats subjected to ovarian hormone deprivation.

Here we investigated the effects of physical training on cardiovascular autonomic control and cardiac morphofunctional parameters in spontaneously hypertensive rats (SHRs) subjected to ovarian hormone deprivation. Forty-eight 10-week-old SHRs were divided into two groups: ovariectomized (OVX, n=24) and sham (SHAM, n=24). Half of each group (n=12) was trained by swimming for 12 weeks (OVX-T and SHAM-T). Cardiac morphology and functionality were assessed using echocardiography, and autonomic parameters were assessed using double pharmacological autonomic block, baroreflex sensitivity (BRS), and analyses of heart rate variability (HRV) and blood pressure variability (BPV). Ovariectomy did not influence the cardiac autonomic tonus balance unlike physical training, which favored greater participation of the vagal autonomic tonus. Ovariectomy and aerobic physical training did not modify HRV and BRS, unlike BPV, for which both methods reduced low-frequency oscillations, suggesting a reduction in sympathetic vascular modulation. Untrained ovariectomized animals showed a reduced relative wall thickness (RWT) and increased diastolic and systolic volumes and left ventricular diameters, resulting in increased stroke volume. Trained ovariectomized animals presented reduced posterior wall thickness and RWT as well as increased final diastolic diameter, left ventricular mass, and stroke volume. Ovarian hormone deprivation in SHRs promoted morphofunctional adaptations but did not alter the evaluation of cardiac autonomic parameters. In turn, aerobic physical training contributed to a more favorable cardiac autonomic balance to the vagal autonomic component and promoted morphological adaptations but had little effect on cardiac functionality.

Cardiovascular physiology and autonomic heart control principles: the use of a station rotation strategy to recall basic cardiovascular knowledge among exercise science students

Aim: Cardiovascular physiology learned by exercise science students is often quickly forgotten. We tested whether a state rotation model would help students to recall key principles of Cardiovascular Physiology (CV). Methods: Seventy-one undergraduate students enrolled in the Exercise Physiology Course at the School of Physical Education and Sport, University of São Paulo, participated in the study. The students were randomly assigned into one of 4 stations, dedicated to recalling the concepts of the heart as a pump (e.g. preload, post-load, and contractility; station 1) and hemodynamics (e.g. serial and parallel conductance; station 2) by using the educational tool. Heart rate (HR) control by sympathetic nervous system activation (station 3) and HR control by vagal activation (station 4) were assessed by quantifying HR response to the Stroop color and word test and during face immersion in cold water, respectively. To evaluate the efficacy of the intervention, we used a Socrative app to launch eight multiple-choice questions before (PRE) and after (POST) the student's station rotation. The questions were related to the basic principles of exercise physiology and its consequences on the cardiovascular system. Results: The 4-station average score (% of corrected answers) achieved after the station rotation was higher than the score achieved before (71.21%, SD 14.50 vs. 31.07%, SD 18.04; for POST and PRE, respectively p < 0.005). Considering specific stations, the lowest score of corrected answers before the rotation was observed at station 2- hemodynamics when compared with station 1-heart as a pump and station 3/4 - autonomic control (18.9%, SD 0.9 vs. 46.5, SD 24.1 and 34.8, SD 2.1 for hemodynamics, heart as a pump and autonomic control, respectively). Interestingly, after the rotation, there was a significant increase in corrected scores for all stations (33.9, SD 9.8; 80.5, SD 4.6 and 90.2, SD 2.3, for hemodynamics, heart as a pump, and autonomic control, respectively). Conclusion: Our results suggest that the use of the educational tool was effective to recall CV principles that are essential to a better understanding of the CV responses to exercise and applying the concepts in exercise testing and prescription for different populations.

The renin-angiotensin system and cardiovascular autonomic control in aging

Aging is the greatest independent risk factor for developing hypertension and cardiovascular-related diseases including systolic hypertension, vascular disease, ischemic events, arrhythmias, and heart failure. Age-related cardiovascular risk is associated with dysfunction of peripheral organ systems, such as the heart and vasculature, as well as an imbalance in the autonomic nervous system characterized by increased sympathetic and decreased parasympathetic neurotransmission. Given the increasing prevalence of aged individuals worldwide, it is critical to better understand mechanisms contributing to impaired cardiovascular autonomic control in this population. In this regard, the renin-angiotensin system has emerged as an important hormonal modulator of cardiovascular function in aging, in part through modulation of autonomic pathways controlling sympathetic and parasympathetic outflow to cardiovascular end organs. This review will summarize the role of the RAS in cardiovascular autonomic control during aging, with a focus on current knowledge of angiotensin II versus angiotensin-(1−7) pathways in both rodent models and humans, pharmacological treatment strategies targeting the renin-angiotensin system, and unanswered questions for future research.

Relationships Between Cardiovascular Autonomic Profile and Work Ability in Patients With Pure Autonomic Failure.

Pure autonomic failure (PAF) is a rare disorder belonging to the group of synucleinopathies, characterized by autonomic nervous system degeneration. Severe orthostatic intolerance with recurrent syncope while standing are the two most disabling manifestations. Symptoms may start at middle age, thus affecting people at their working age. The aims of this study were to evaluate the autonomic and work ability impairment of a group of PAF patients and assess the relationships between cardiovascular autonomic control and work ability in these patients. Eleven PAF patients (age 57.3 ± 6.7 years), engaged in work activity, participated in the study. They completed the Composite Autonomic Symptom Score (COMPASS-31, range 0 no symptom-100 maximum symptom intensity) and Work Ability questionnaires (Work Ability Index, WAI, range 7–49; higher values indicate better work ability and lower values indicating unsatisfactory or jeopardized work ability). Electrocardiogram, blood pressure and respiratory activity were continuously recorded for 10 min while supine and during 75° head-up tilt (HUT). Autoregressive spectral analysis of cardiac cycle length approximated as the time distance between two consecutive R-wave peaks (RR) and systolic arterial pressure (SAP) variabilities provided the power in the high frequency (HF, 0.15–0.40 Hz) and low frequency (LF, 0.04–0.15 Hz) bands of RR and SAP variabilities. Cardiac sympatho-vagal interaction was assessed by LF to HF ratio (LF/HF), while the LF power of SAP (LFSAP) quantified the vascular sympathetic modulation. Changes in cardiovascular autonomic indexes induced by HUT were calculated as the delta (Δ) between HUT and supine resting positions. Spearman correlation analysis was applied. PAF patients were characterized by a moderate autonomic dysfunction (COMPASS-31 total score 47.08 ± 20.2) and by a reduction of work ability (WAI 26.88 ± 10.72). Direct significant correlations were found between WAI and ΔLFRR (r = 0.66, p = 0.03) and ΔLF/HFRR (r = 0.70, p = 0.02). Results indicate that patients who were better able to modulate heart rate, as revealed by a greater cardiac sympathetic increase and/or vagal withdrawal during the orthostatic stimulus, were those who reported higher values of WAI. This finding could be relevant to propose new strategies in the occupational environment to prevent early retirement or to extend the working life of these patients.

Effects of transcutaneous auricular vagus nerve stimulation on cardiovascular autonomic control in health and disease.

Autonomic nervous system (ANS) dysfunction is a well-known feature of cardiovascular diseases (CVDs). Studies on heart rate variability (HRV), a non-invasive method useful in investigating the status of cardiovascular autonomic control, have shown that a predominance of sympathetic modulation not only contributes to the progression of CVDs but has a pivotal role in their onset. Current therapies focus more on inhibition of sympathetic activity, but the presence of drug-resistant conditions and the invasiveness of some surgical procedures are an obstacle to complete therapeutic success. On the other hand, targeting the parasympathetic branch of the autonomic nervous system through invasive vagus nerve stimulation (VNS) has shown interesting results as alternative therapeutic approach for CVDs. However, the invasiveness and cost of the surgical procedure limit the clinical applicability of VNS and hinder the research on the physiological pathway involved. Transcutaneous stimulation of the auricular branch of the vagus nerve (tVNS) seems to represent an important non-invasive alternative with effects comparable to those of VNS with surgical implant. Thus, in the present narrative review, we illustrate the main studies on tVNS performed in healthy subjects and in three key examples of CVDs, namely heart failure, hypertension and atrial fibrillation, highlighting the neuromodulatory effects of this technique.

Does COVID‐19 influence the sympathetic regulation of blood pressure?

Does COVID‐19 influence the sympathetic regulation of blood pressure?

Use of Mayer wave activity to demonstrate aberrant cardiovascular autonomic control following sports concussion injury.

Dysregulation of cardiovascular autonomic control is gaining recognition as a prevailing consequence of concussion injury. Characterizing the presence of autonomic dysfunction in concussed persons is inconsistent and conventional metrics of autonomic function cannot differentiate the presence/absence of injury. Mayer wave (MW) activity originates through baroreflex adjustments to blood pressure (BP) oscillations that appear in the low‐frequency (LF: 0.04–0.15 Hz) band of the BP and heart rate (HR) power spectrum after a fast Fourier transform. We prospectively explored MW activity (∼0.1 Hz) in 19 concussed and 19 noninjured athletes for 5 min while seated at rest within 48 h and 1 week of injury. MW activity was derived from the LF band of continuous digital electrocardiogram and beat‐to‐beat BP signals (LFHR, LF‐SBP, MWHR, and MW‐SBP, respectively); a proportion between MWBP and MWHR was computed (cMW). At 48 h, the concussion group had a significantly lower MWBP and cMW than controls; these differences were gone by 1 week. MWHR, LFHR, and LF‐SBP were not different between groups at either visit. Attenuated sympathetic vasomotor tone was present and the central autonomic mechanisms regulating MW activity to the heart and peripheral vasculature became transiently discordant early after concussion with apparent resolution by 1 week.

Interaction between Autonomic Regulation, Adiposity Indexes and Metabolic Profile in Children and Adolescents with Overweight and Obesity.

Early obesity predicts initial modifications in cardiac and vascular autonomic regulation. The aim of this study was to assess the possible interaction between non-invasive measures of autonomic cardiovascular control and peripheral endothelium regulation in children with overweight and obesity. We involved 114 young subjects (77M/37F, 12.7 ± 2.2 years) with normal weight (NW, n = 46) to overweight or obesity (OB, n = 68). Multivariate statistical techniques utilizing a collection of modern indices of autonomic regulation, adiposity indexes and metabolic profile were employed. Resting values show substantial equivalence of data. Conversely, blood pressure variance is greater in NW/OB groups. The correlation matrix between major autonomic and metabolic/hemodynamic variables shows a clustered significant correlation between homogeneous indices. A significant correlation between metabolic indices and endothelial and autonomic control, mostly in its vascular end, was recorded. Particularly, the alpha index is significantly correlated with triglycerides (r = −0.261) and endothelial indices (RHI, r = 0.276). Children with obesity show a link between indices of autonomic and endothelial function, fat distribution and metabolic profile. The optimization of autonomic control, for instance by exercise/nutrition interventions, could potentially prevent/delay the occurrence of structural vascular damage leading to reduced cardiovascular health.

The interplay between heated environment and active standing test on cardiovascular autonomic control in healthy individuals

Objective. To investigate the interplay between active standing and heat stress on cardiovascular autonomic modulation in healthy individuals. Approach. Blood pressure (BP) and ECG were continuously recorded during 30 min in supine (SUP) and 6 min in orthostatic position (ORT) under thermal reference (TC; ∼24 °C) or heated environment (HOT; ∼36 °C) conditions, in a randomized order. All data collection was performed during the winter and spring seasons when typical outdoor temperatures are ∼23 °C. Spectral analysis was employed by the autoregressive model of R–R and systolic blood pressure (SBP) time series and defined, within each band, in low (LF, 0.04 to 0.15 Hz) and high (0.15–0.40 Hz) frequencies. The indices of cardiac sympathetic (LF) and cardiac parasympathetic (HF) were normalized (nu) dividing each band power by the total power subtracted the very-low component (<0.04 Hz), obtaining the cardiac autonomic balance (LF/HF) modulation. The gain of the relationship between SBP and R–R variabilities within the LF band was utilized for analysis of spontaneous baroreflex sensitivity (alpha index; αLF). Nonlinear analysis was employed through symbolic dynamics of R–R, which provided the percentage of sequences of three heart periods without changes in R–R interval (0V%; cardiac sympathetic modulation) and two significant variations (2UV% and 2LV%; cardiac vagal modulation). Main results. HOT increased 0V% and HR, and decreased αLF and 2UV% during SUP compared to TC. During ORT, HOT provokes a greater increment on HR, LF/HF and 0V%, indexes compared to ORT under TC. Significance. At rest, heat stress influences both autonomic branches, increasing sympathetic and decreasing vagal modulation and spontaneous baroreflex sensitivity. The augmented HR during active standing under heat stress seems to be mediated by a greater increment in cardiac sympathetic modulation, showing an interplay between gravitational and thermal stimulus.

Can Dyssynergia of Vestibulosympathetic and Baroreflexes Cause Vestibular Syncope? The Hypothesis Based on the Velocity-Storage Function.

The mechanism of vestibular syncope, the syncope occurring during the vertigo attacks, remains uncertain. This study aims to clarify the mechanism of vestibular syncope by pursuing the function of vestibular system in cardiovascular autonomic control and by defining neuro-hemodynamic changes in vestibular syncope. By integrating the velocity-storage (VS) circuit in the brainstem and cerebellum, we propose that the vestibular syncope develops as a result of dyssynergia of the vestibulosympathetic and baroreflexes in which centrally estimated downward inertial acceleration during the vertigo attacks acts as a trigger. Recognition of the vestibular disorders as a possible cause of syncope would allow proper managements for prevention of further syncope and related complications in patients with vestibular disorders.

Cardiovascular autonomic neuropathy in diabetes: Pathophysiology, clinical assessment and implications.

Cardiovascular autonomic neuropathy (CAN) is a debilitating condition that mainly occurs in long-standing type 2 diabetes patients but can manifest earlier, even before diabetes is diagnosed. CAN is a microvascular complication that results from lesions of the sympathetic and parasympathetic nerve fibers, which innervate the heart and blood vessels and promote alterations in cardiovascular autonomic control. The entire mechanism is still not elucidated, but several aspects of the pathophysiology of CAN have already been described, such as the production of advanced glycation end products, reactive oxygen species, nuclear factor kappa B, and pro-inflammatory cytokines. This microvascular complication is an important risk factor for silent myocardial ischemia, chronic kidney disease, myocardial dysfunction, major cardiovascular events, cardiac arrhythmias, and sudden death. It has also been suggested that, compared to other traditional cardiovascular risk factors, CAN progression may have a greater impact on cardiovascular disease development. However, CAN might be subclinical for several years, and a late diagnosis increases the mortality risk. The duration of the transition period from the subclinical to clinical stage remains unknown, but the progression of CAN is associated with a poor prognosis. Several tests can be used for CAN diagnosis, such as heart rate variability (HRV), cardiovascular autonomic reflex tests, and myocardial scintigraphy. Currently, it has already been described that CAN could be detected even during the subclinical stage through a reduction in HRV, which is a non-invasive test with a lower operating cost. Therefore, considering that diabetes mellitus is a global epidemic and that diabetic neuropathy is the most common chronic complication of diabetes, the early identification and treatment of CAN could be a key point to mitigate the morbidity and mortality associated with this long-lasting condition.

Hypoglycemia Impairs Baroreflex Sensitivity: Implications for Autonomic Control of Cardiovascular Function in Diabetes

Background: Iatrogenic hypoglycemia is an unintended, though common, occurrence in individuals with diabetes. There is a clear association between hypoglycemia exposure and an increase in mortality in individuals with type 2 diabetes (T2DM). It is well-established that recurrent hypoglycemic episodes impair the counterregulatory hormone responses; however, it is yet to be determined if in T2DM there are more global effects of hypoglycemia on autonomic control of cardiovascular function (baroreflex sensitivity, BRS), as has been shown in healthy individuals. This is a clinically relevant knowledge gap as decreases in BRS are pro-arrhythmogenic and associated with decreases in mortality in individuals with diabetes. Objective: We tested the hypothesis that in individuals with T2DM, hypoglycemia impairs baroreflex sensitivity (BRS), a robust measure of cardiovascular autonomic control. Methods: Individuals with well-controlled T2DM and without known cardiovascular disease were exposed to two 90-minute episodes of experimental hypoglycemia (50 mg/dl) in the same day. All individuals experienced a hypoglycemic-hyperinsulinemic clamp in the morning (AM clamp) and again in the afternoon (PM clamp). BRS was assessed using the modified Oxford method (sequential administration of nitroprusside and phenylephrine) before the initiation of each hypoglycemic-hyperinsulinemic clamp, during the last 30 minutes of hypoglycemia, and the following day. Results: The study included 16 individuals with a diagnosis of T2DM (6 men and 10 women) with the following characteristics (mean ± SD): age 45 ± 11 years, BMI 32 ± 6 kg/m2, hemoglobin A1c 6.4 ± 0.9%, and diabetes duration 8 ± 5 years. At baseline, individuals with T2DM had a BRS of 7.7 ± 3.6 ms/mmHg, which is reduced compared to a BRS of 21.3 ± 13.8 ms/mmHg in a historical healthy control group of 54 subjects (p<0.001). A mixed effects model adjusting for sex, age, BMI, and insulin level, demonstrated a significant effect of hypoglycemia on BRS (p=0.008). Pairwise comparisons revealed a significant decrease in BRS during the PM clamp as compared with BRS assessed at baseline (5.5 ± 5.0 vs 7.7 ± 3.6 ms/mmHg, p=0.045), during the AM clamp (5.5 ± 5.0 vs 10.5 ± 5.6 ms/mmHg, p=0.43), and the following day (5.5 ± 5.0 vs 8.6 ± 3.8 ms/mmHg, p=0.33). Of note, there was no significant difference between BRS at baseline and during the AM clamp (p=0.44). Additionally, insulin levels positively and strongly correlated with BRS at baseline (R2 0.52) and during the AM clamp (R2 0.67). Discussion: Insulin may have a stimulatory effect on BRS during a hyperinsulinemic hypoglycemic clamp that counters the inhibitory effect of hypoglycemia during the first episode of hypoglycemia. However, with exposure to a second hypoglycemic clamp, BRS decreases. Conclusion: Individuals with T2DM have low BRS at baseline, which is further reduced after 2 episodes of hypoglycemia.

Functional Dissection of PVN MC4R Neural Pathway in Autonomic and Cardiovascular Functions

Central melanocortin pathways, mainly via acting on melanocortin-4 receptor (MC4R), play an important role in both energy homeostasis and sympathetic control of cardiovascular function. The paraventricular nucleus of hypothalamus (PVN) is one of hypothalamic nuclei with highest MC4R expression and is well known for its role in metabolic and autonomic regulations; however, the role of PVN-MC4R neural pathways in this regard remains incompletely understood. In this study, we first tested whether chemogenetic activation of PVN-MC4R neurons affects cardiovascular function. Adeno-associated virus (AAV) expressing excitatory (hM3Dq) Designer Receptors Exclusively Activated by Designer Drugs (DREADD) receptors were directly injected into the PVN of MC4R-Cre knock-in mice that are implanted with radio-telemetry for chronic monitoring of blood pressure. DREADD activation of PVN-MC4R neurons significantly elevated mean arterial pressure and heart rate. Next, we prepared a separate group of mice and subjected them to a battery of tests to gain insight into the role of these neurons in other behavioral and physiological regulations. Whole-body infrared thermal imaging upon DREADD activation of PVN-MC4R neurons revealed significant increase of temperature in near neck region, lower back, and tail. Behavioral monitoring in PhenoTyper cage further showed that DREADD activation of PVN-MC4R neurons leads to hypoactivity, suppressed feeding, and trend toward increased drinking behavior. In order to gain further insight into the neuroanatomical organization of PVN-MC4R neurons, we comprehensively mapped afferent projections of PVN-MC4R neurons by stereotaxically delivering Cre-dependent AAV driving expression of eYFP into the PVN of MC4R-Cre mice, which revealed a broad innervation of PVN-MC4R neurons to the brain regions that are known to be important for metabolic homeostasis and autonomic-cardiovascular control, including but not limited to parabrachial nucleus, nucleus of solitary tract, ventrolateral medulla, and spinal cord. Additionally, using a combination of sophisticated viral tools, we also mapped the brain regions where neurons provide monosynaptic inputs to PVN-MC4R neurons. In addition to the brain regions in which neurons are known to send monosynaptic inputs to PVN-MC4R neurons, such as arcuate nucleus, few discreate presynaptic neurons were also observed in organum vasculosum of the lamina terminalis, bed nucleus of the stria terminalis, supraoptic nucleus (SON) and ventral subiculum (vSub). These results provide an important insight into the neuroanatomical organization and multifaceted role of PVN-MC4R neural pathways in behavioral and physiological regulations.

Short-Term Effect of Percutaneous Coronary Intervention on Heart Rate Variability in Patients with Coronary Artery Disease

Myocardial ischemia in patients with coronary artery disease (CAD) leads to imbalanced autonomic control that increases the risk of morbidity and mortality. To systematically examine how autonomic function responds to percutaneous coronary intervention (PCI) treatment, we analyzed data of 27 CAD patients who had admitted for PCI in this pilot study. For each patient, five-minute resting electrocardiogram (ECG) signals were collected before and after the PCI procedure. The time intervals between ECG collection and PCI were both within 24 h. To assess autonomic function, normal sinus RR intervals were extracted and were analyzed quantitatively using traditional linear time- and frequency-domain measures [i.e., standard deviation of the normal-normal intervals (SDNN), the root mean square of successive differences (RMSSD), powers of low frequency (LF) and high frequency (HF) components, LF/HF] and nonlinear entropy measures [i.e., sample entropy (SampEn), distribution entropy (DistEn), and conditional entropy (CE)], as well as graphical metrics derived from Poincaré plot [i.e., Porta’s index (PI), Guzik’s index (GI), slope index (SI) and area index (AI)]. Results showed that after PCI, AI and PI decreased significantly (p < 0.002 and 0.015, respectively) with effect sizes of 0.88 and 0.70 as measured by Cohen’s d static. These changes were independent of sex. The results suggest that graphical AI and PI metrics derived from Poincaré plot of short-term ECG may be potential for sensing the beneficial effect of PCI on cardiovascular autonomic control. Further studies with bigger sample sizes are warranted to verify these observations.

English

Fibromyalgia is a disease characterized by conical pain associated with autonomic dysregulation of the sufferer, without many treatment alternatives. The objective of this study was to find out the relationship between physical exercise in an aquatic environment, pain perception and cardiovascular autonomic control in adult women suffering from fibromyalgia. The sample consisted of 15 women diagnosed with fibromyalgia who participated in 24 40-minute exercise sessions in a water environment. Anthropometric measures, heart rate variability (HRV) and pain perception (PCS) were evaluated in four experimental times (t1, baseline; t2, session 8; t3, session 16; t4, session 24). In addition, the perception of pain was evaluated in each session through VAS. The results show that the perception of pain through VAS decreased when comparing all the means evaluated before and after each session (p &lt;0.05). In the PCS application, a lower Total Pain and Rumination was obtained when comparing t1 with t4. HRV values showed that SDNN and RMSSD were higher after the session, when t4 was compared with t1 (p &lt;0.05). The mean heart rate decreased at the end of the sessions, showing a better adaptation to exercise. The relationship between pain and cardiac measurements was given by a positive correlation in the pain domains recorded before the sessions and the RMSSD and SDNN values. In conclusion, the practice of physical exercise in an aquatic environment would indicate a lower perception of pain and a better cardiac autonomic response in women with fibromyalgia.

Cardiovascular Autonomic Control, Sleep and Health Related Quality of Life in Systemic Sclerosis.

Chronic pain and dysautonomic symptoms deteriorate Systemic sclerosis (SSc) patients’ health-related quality of life with serious repercussions on social life and even on sleep. Heart Rate Variability (HRV) analysis can identify cardiovascular autonomic control impairment in subclinical condition. The aim of the present observational cross-sectional study was to assess the relationship between dysautonomic symptoms, quality of life status and cardiovascular autonomic profile. ECG and respiration were recorded at rest in 20 SSc patients. HRV analysis was performed using two different approaches: Linear spectral analysis and non-linear symbolic analysis. Pain was evaluated using the Numeric Rating Scale (NRS) and 3 questionnaires were administered for the evaluation of sleep quality (PSQI), mood tone (PHQ-9) and disability (HAQ). We found that sleep impairment was related to sympathetic predominance at rest measured as low-frequency/high-frequency ratio (LF/HF) (r = 0.48 and p = 0.033); poorer sleep quality was related to higher pain values (r = 0.48 and p = 0.034) and depressive symptoms (r = 0.82 and p < 0.01); higher pain scores were related to higher cardiovascular vagal modulation and higher disability indexes (r = 0.47 and p = 0.038 & r = 0.55 and p = 0.012, respectively). In conclusion dysautonomia and chronic pain showed a severe impact on sleep quality and disability with a consequent worsening of depressive symptom in our cohort of SSc patients.

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.

Correlation of staging and risk factors with cardiovascular autonomic neuropathy in patients with type II diabetes mellitus

The impairment of cardiovascular autonomic control among the underdiagnosed complication of diabetes mellitus (DM) with a high prevalence rate of up to 60% in type 2 DM (T2DM). Cardiac autonomic neuropathy (CAN) is an independent risk factor for cardiovascular mortality, arrhythmia, silent ischemia, any major cardiovascular event, and heart failure. We aimed to evaluate cardiovascular autonomic activity by different physiological maneuvers, study risk factors for diabetic CAN including age, gender, duration of diabetes, body mass index (BMI), and glycemic control, and correlate CAN stage with risk factors. One hundred and forty-two T2DM patients consisted of 62 males and 80 females and 100 volunteers as a control sample. Cardiac autonomic functions were assessed by Ewing's tests. Glycated hemoglobin (HbA1c), body weight, height, body mass index (BMI), and waist-hip ratio (WHR) were also measured. Cardiovascular autonomic functions and Ewing scores were significantly different in people with diabetes when compared with control healthy subjects. Ewings test values and Ewing scores were significantly different between diabetics with and without CAN and within patients with different CAN staging. People with diabetes with CAN have a significantly longer duration of disease when compared to those without CAN. A strong association has been found between CAN severity and patient age, duration of disease, HbA1c severity, and the WHR (P < 0.001) but not with BMI. The duration of disease and HbA1c level appear to be associated with the development of CAN (P = 0.001 and P = 0.008, respectively). The poorer glycemic control and the longer the duration of the disease, the higher the prevalence of CAN in T2DM. Age, duration of disease, WHR, and HbA1c are well correlated with the severity of CAN. Parasympathetic impairment is more sensitive to the detection of autonomic dysfunctions than do sympathetic impairment.