Greater Sympathetic Activation Research Articles

Orthostatic test showshighersystolic blood pressure andsympathetic response in uncomplicated type1 diabetespatients with normal V̇O2maxvs. healthy controls.

Cardiovascular autonomic neuropathy remains underdiagnosed in type1 diabetes mellitus, posing a risk for severe complications, particularly in patients with lowered V̇O2max, compared to controls. This study aimed to determine whether heart rate variability during cardiovascular autonomic reflex tests reveals early signs of cardiovascular autonomic neuropathy in patients with uncomplicated type1 diabetes mellitus and normal cardiovascular fitness, compared to healthy controls. A type1 diabetes mellitus group (n = 14) with no other diagnosed diseases (diabetes duration 15 ± 7years) and a control group (n = 31) underwent deep breathing test, passive orthostatic test, and cardiopulmonary exercise test. Participants were assessed for heart rate variability, heart rate, blood pressure, and V̇O2max (mL/min/kg). Participant characteristics, including V̇O2max (mL/min/kg), showed no significant differences. The type1 diabetes mellitus group had higher systolic blood pressure during the supine phase of the orthostatic test than healthy controls (131.6 ± 14.7mmHg vs. 122.4 ± 10.8mmHg, p = 0.022). After 5mins in the upright position, systolic blood pressure (132.2 ± 20.6mmHg vs. 118.7 ± 11.7mmHg, p = 0.036), heart rate (85 (76; 89) bpm vs. 75 (72; 83) bpm, p = 0.013), and the root mean square of successive RR interval differences (20.22 (11.22; 27.42) vs. 27.11 (19.90; 35.52), p = 0.033) were significantly different compared to controls. Patients with uncomplicated type1 diabetes mellitus, despite having normal cardiorespiratory fitness, exhibited higher systolic pressure and greater sympathetic activation in orthostatic tests, suggesting subclinically altered cardiovascular autonomic function.

Clinical and Autonomic Profile, and Modified Calgary Score for Children and Adolescents with Presumed Vasovagal Syncope Submitted to the Tilt Test.

In the pediatric population, syncope is mainly from vasovagal (VVS) origin. Its evaluation must be done by clinical methods, and the tilt test (TT) can contribute to the diagnosis. To analyze the clinical profile, Calgary and modified Calgary scores, response to TT and heart rate variability (HRV) of patients aged ≤ 18 years with presumed VVS. To compare the variables between patients with positive and negative responses to TT. Observational and prospective study, with 73 patients aged between 6 and 18 years, submitted to clinical evaluation and calculation of scores without previous knowledge of the TT. It was done at 70º under monitoring for HRV analysis. P-value < 0.05 was the statistical significance criterion. Median age was 14.0 years; 52% of participants were female, 72 had Calgary ≥ -2 (mean 1.80), and 69 had modified Calgary ≥ -3 (mean 1.38). Prodromes were observed in 59 patients, recurrence in 50 and trauma in 19. The response to TT was positive in 54 participants (49 vasovagal, with 39 vasodepressor responses), with an increase in the low frequency (LF) component and a decrease in the high frequency (HF) component (p < 0,0001). In the supine position, LF was 33.6 in females and 47.4 in normalized units for males (p = 0.02). When applying the operating characteristic curve for positive TT, there was no statistical significance for HRV and scores. Most children and adolescents with a presumed diagnosis of VVS presented a typical clinical scenario, with a Calgary score ≥ -2, and a predominant vasodepressor response to TT. Greater sympathetic activation was observed in the supine position in males. Calgary scores and sympathetic activation did not predict the response to TT.

Retrospective analysis of autonomic dysfunction in epilepsy patients from neurophysiological recordings

Autonomic dysfunction is often associated with seizures in patients with epilepsy. Autonomic dysfunction during seizures can cause serious events like cardiac arrest and sudden unexplained death. Early detection of autonomic dysfunction is crucial to avoid such medical emergencies. In our study, we analyzed the heart rate variability (HRV) in physiological recording during the preictal, ictal and postictal periods. A total of 142 seizures with various semiologies recorded from 49 epilepsy patients were included. Time-domain measurements including mean hear rate (HR), RR interval (RRI), root-mean-square of successive R-R interval differences (RMSSD), The standard deviation of N-N intervals (SDNN) and percentage of successive RR intervals that differ by more than 50 ms(pNN50) were analyzed at different time points, 20 minutes before the seizure, 1 minute before the seizure, during the seizure and 20 minutes after the seizure. We observed there was a significant difference in HRV parameters during and just before the seizure onset (RMSSD with p-value&lt;0.001 and SDNN with p-value&lt;0.001). We also observed that there was a suppression of parasympathetic activity and activation of sympathetic stimulation in the ictal and peri-ictal period, which was characterized by an elevation in the mean heart rate (HR), whereas the mean RRI showed an inversely proportional trend. There was a reduction in mean RMSSD, SDNN and pNN50 prior to seizure onset and was more pronounced in generalized seizures as compared to focal seizures with preserved or impaired awareness. There was a greater sympathetic activation and parasympathetic inhibition during an epileptic seizure in females as compared to male patients. These findings suggest that autonomic dysregulation was increased during a generalized seizure when compared to a focal seizure. HRV analysis can be used as a valid method for quantifying central influences on the autonomic nervous system and its cardiac control. A major advantage of electrocardiogram (ECG)-based seizure detection is that the ECG is an essentially easier signal to obtain, with a higher signal-to-noise ratio than EEG (electroencephalogram). Based on the inferences from this study future studies could be done to build machine learning models which could form the base for the development of wearable seizure prediction devices.

Impact of victory and defeat on the perceived stress and autonomic regulation of professional eSports athletes.

Competitive sports involve physiological, technical and psychological skills, which influence directly on individuals’ performance. This study aims to investigate the levels of perceived stress and Heart Rate Variability (HRV) before and after matches with victory and defeat in professional eSports athletes. Our hypothesis was that the winners would have better autonomic and stress responses after match, thus corroborating the literature on neurocardiac connections. Fifty male eSport players were selected players from 10 different Brazilian teams. The experiment was carried out in 2 sessions. Firstly, after signing the informed consent form, 24 h before the game, anthropometric, physical activity levels and time of expertise data were recorded only for sample characterization and the players were familiarized with the perceived stress scale—10 (PSS-10) and the HRV measurements. Secondly, players performed the PSS-10 and HRV recording at rest by 10 min 60 and 30 min before the game (i.e., baseline time) and 10 min after the end of the game. Overall, concerning PSS-10 our findings show that VG had significant reduced scores in post-game time compared to baseline (BL) and pre-game times, while DG had significant increased scores in post-game time compared to BL and pre-game times. Regarding HRV, our results demonstrate that VG had significant increase in RR, SDNN, rMSSD, pNN50 and HF, and significant decrease in LF and LF/HF, while DG had a significant decrease in RR, SDNN, rMSSD and HF, and significant increase in LF and LF/HF. It was observed that VG had better HRV responses (greater parasympathetic activation) as well as lower levels of perceived stress, while DG had worst HRV responses (greater sympathetic activation) and higher levels of perceived stress.

Cardioautonomic control in healthy singleton and twin pregnancies.

In conjunction with significant cardiovascular adaptation, changes in cardioautonomic balance, specifically greater sympathetic activation and vagal withdrawal, are considered normal adaptations to healthy singleton pregnancy. Cardiovascular adaptation to twin pregnancy is more profound than that of singleton pregnancies; however, the changes in cardioautonomic control during multifetal gestation are unknown. To address this gap, beat-by-beat blood pressure (photoplethysmography) and heart rate (lead II electrocardiogram) were measured continuously in 25 twin pregnancies and 25 singleton pregnancies (matched for age, prepregnancy body mass index, and gestational age) during 10 min of rest. Data extracted from a 3- to 5-min period were used to analyze heart rate variability (HRV), blood pressure variability (BPV), cardiovagal baroreflex gain, and cardiac intervals as indicators of cardioautonomic control. Independent t tests were used to determine statistical differences between groups (α = 0.05), and the false rate discovery was determined to adjust for multiple comparisons. Resting heart rate was greater in twin compared with singleton pregnancies (91 ± 10 vs. 81 ± 10 beats/min; P = 0.001), but blood pressure was not different. Individuals with twin pregnancies had lower HRV, evidenced by lower standard deviation of R-R intervals (32 ± 11 vs. 47 ± 18 ms; P = 0.001), total power (1,035 ± 810 vs. 1,945 ± 1,570 ms2; P = 0.004), and high frequency power (224 ± 262 vs. 810 ± 806 ms2; P < 0.001) compared with singleton pregnancies. There were no differences in cardiac intervals, BPV, and cardiovagal baroreflex gain between groups. Our findings suggest that individuals with twin pregnancies have greater sympathetic and lower parasympathetic contributions to heart rate and that cardiac, but not vascular, autonomic control is impacted during twin compared with singleton pregnancy.NEW & NOTEWORTHY Individuals with healthy twin pregnancies had lower overall heart rate variability compared with those with singleton pregnancies at similar gestational ages. These results suggest a greater sympathetic and reduced parasympathetic contribution to cardiac control in twin pregnancies. Baseline heart rate was elevated, while arterial pressure and spontaneous cardiovagal baroreflex gain were not different between groups. This was result of the upward resetting of the cardiovagal baroreflex during healthy twin pregnancy, thus maintaining arterial pressure.

Target Behavioral Response Analyses for the Development of Delay Munitions: Obscuring Fog for Non-lethal Anti-personnel Landmines

This experiment explores the utility of visual obscuration as a method for creating non-lethal munitions that can delay an adversary’s removal of anti-vehicle mines. Visual obscuration was achieved using controlled levels of artificial fog. Twenty-four subjects searched for mines under laboratory conditions of baseline no fog, low-lying fog, and immersive fog. A .52 or greater obscuration was associated with an 85% suppression mine detection. Under fog, subjects detected most mines by accidental kicking and found them in an average of 5 min compared with under 3 s with no fog. The fog created a condition of heightened stress, as reflected by evidence of increased sympathetic activity indexed by increased heart rate and increased electrodermal activity. Immersive fog showed greater sympathetic activation in subjects as indexed by more frequent electrodermal responses and twice the number of instances of giving up compared with the low-lying fog.

Modulación de las respuestas fisiológicas ante estímulos afectivos: una herramienta para investigar procesos psicológicos

El estudio de los procesos psicológicos suele realizarse a partir de medidas de autorreporte y, en algunos casos, a través de tareas conductuales. Sin embargo, cada vez es más necesario obtener medidas más precisas y objetivas de las respuestas psicológicas para fortalecer las conclusiones de los estudios y su alcance. Por lo anterior, el objetivo del presente estudio fue analizar los cambios en distintas respuestas fisiológicas ante estímulos con diferente contenido afectivo, para obtener indicadores fisiológicos de los procesos atencionales, emocionales y motivacionales. Se registraron las respuestas de 40 participantes mientras observaban estímulos apetitivos, neutrales y aversivos. Los resultados muestran que los estímulos apetitivos y aversivos generan mayor respuesta de conductividad de la piel, lo que indica mayor activación simpática y mayor respuesta de orientación, así como mayor desaceleración de la tasa cardiaca y mayor inhibición prepulso, lo que sugiere una mayor respuesta atencional. También se encontró que los estímulos aversivos potencian el reflejo de sobresalto y los apetitivos lo inhiben, lo que lo convierte en un marcador fisiológico de la respuesta motivacional. No se encontraron diferencias significativas entre hombres y mujeres. En conjunto, los resultados apoyan el uso de estas metodologías para el estudio de la orientación/atención, la emoción y la motivación.

Acute effects of autoadjusting and fixed continuous positive airway pressure treatments on cardiorespiratory coupling in obese patients with obstructive sleep apnea

BackgroundTreatment with positive airway pressure devices improved signs and symptoms of obstructive sleep apnea syndrome (OSA); however, auto-adjusting positive pressure (APAP) device was not as effective as continuous positive airway pressure (CPAP) in reducing arterial blood pressure and insulin resistance. The role played by autonomic cardiac regulation remains to be clarified.We aimed to test the effects of CPAP and APAP on autonomic regulation and cardiorespiratory coupling during sleep. MethodsWe retrospectively analyzed full-night polysomnographic studies. 19 patients newly diagnosed with severe OSA (AHI>30) and 7 obese subjects without OSA (CON) were enrolled. Each OSA subject was assigned to CPAP or APAP treatment and underwent a sleep study after 1week of treatment. Spectral and cross-spectral analyses of heart rate variability (HRV) and respiration were performed to assess autonomic profile and coherence (K2) between respiration and HF oscillation during sleep in CPAP, APAP and CON groups. ResultsIn CPAP and CON, LFnu and LF/HF, markers of sympathetic modulation, decreased from N2 to N3 and increased during REM sleep (p<0.001), while in APAP group, sympathetic modulation was significantly higher compared with those of CPAP and CON during all sleep stages. K2 values were lower in APAP compared with those in CPAP and CON. ConclusionAPAP treatment was characterized by a greater sympathetic activation and it was associated with a lower cardio-respiratory coupling compared with CPAP. This might account for the different effects on cardiovascular risk factors induced by the two treatments.

Effect of age on the hemodynamic and sympathetic responses at the onset of isometric handgrip exercise

Cardiac and peripheral vasomotor factors contribute to the rapid pressor response at the onset of isometric handgrip exercise. We tested the hypothesis that age enhances the sympathetic and vasoconstrictor response at the onset of isometric handgrip exercise so that the pressor response is maintained, despite a diminished cardiac function. Twelve young and twelve older (24 ± 3 and 63 ± 8 yr) individuals performed 20-s isometric handgrip exercise at 30, 40, or 50% of maximal voluntary contraction force. Muscle sympathetic nerve activity (MSNA) was measured using microneurography. Mean arterial pressure (MAP) and cardiac output (Q) were assessed continuously by finger plethysmography and total peripheral resistance was calculated. MAP increased with the onset of handgrip; this increase was associated with handgrip intensity and was similar in both groups. Heart rate and Q increased with increasing handgrip intensity in both groups, but increases were greater in young vs. older individuals (age × handgrip intensity interaction, P < 0.05). MSNA burst frequency increased (P < 0.01), while MSNA burst incidence tended to increase (P = 0.06) with increasing handgrip intensity in both groups. The change in MSNA between baseline and handgrip, for both frequency and incidence, increased with increasing handgrip intensity for both groups. There was no effect of handgrip intensity or age on total peripheral resistance. The smaller heart rate and Q response during the first 20 s of handgrip exercise in older individuals was not accompanied by a greater sympathetic activation or vasoconstrictor response. However, increases in MAP were similar between groups, indicating that the pressor response at the onset of handgrip exercise is preserved with aging.

Elderly blacks have a similar sympathetic neural responsiveness but greater pressor response to cold stress than elderly whites

Muscle sympathetic nerve activity (MSNA) response to cold stress has been reported to be greater in young blacks than whites. We evaluated whether elderly blacks have greater sympathetic activation during cold stress than age matched whites. MSNA (microneurography), blood pressure (BP), and heart rate (HR) were measured during supine baseline, 2‐min cold pressor test (CPT), and 3‐min of recovery in 10 elderly blacks [age 65 ± 4 (SD) yrs] and 30 elderly whites (69 ± 7 yrs). Mean BP increased during CPT (P &lt; 0.001), while it was greater in blacks than whites at 2 min of CPT (114 ± 21 vs 103 ± 13 mmHg, P = 0.042). HR increased during CPT (P &lt; 0.001) without a group difference (72 ± 7 vs 65 ± 10 mmHg, P = 0.113). MSNA burst frequency, burst incidence, and total MSNA increased during CPT (all P &lt; 0.001). None of these variables showed racial differences during baseline (burst frequency: 51 ± 12 vs 48 ± 10 bursts/min, burst incidence: 77 ± 16 vs 80 ± 15 bursts/100beats, and total MSNA: 781 ± 266 vs 759 ± 241 units) or CPT (63 ± 10 vs 61 ± 10 bursts/min, 88 ± 10 vs 93 ± 8 bursts/100beats, and 1311 ± 636 vs 1476 ± 720 units; all P &gt;; 0.050). Thus, elderly blacks have a greater pressor response to cold stress than elderly whites, which is not attributable to sympathetic neural response. Other vasoconstriction systems (i.e., sympathetic vascular transduction and/or non‐adrenergic vasoconstrictor mechanisms) must be involved.Supported by NIH R01 HL091078.

Fearful temperament and stress reactivity among preschool‐aged children

In this study, we examined the relation between physiological stress-reactivity and temperamental fearfulness in 162 preschool-aged children. Both the autonomic and neuroendocrine arms of the mammalian stress system were examined. Larger stress responses were defined as greater sympathetic activation, parasympathetic withdrawal and cortisol increases to stressor tasks. Fearful temperament was examined using parent report and behavior in response to fear-evocative laboratory tasks. There was little evidence that larger sympathetic activation or parasympathetic withdrawal was associated with fearful temperament. Greater cortisol reactivity, however, was associated with fearful temperament. Additional analyses examined those children who were consistently fearful across all measures, and the results remained largely the same. However, there was some suggestion that consistently fearful compared to non-fearful children might be more likely to exhibit sympathetic activation to the fear-evocative stimuli. These findings provide support for the argument that fearful temperament is associated with greater stress reactivity in young children. Nonetheless the size of the associations was small and future studies will need to determine whether reactivity of stress-sensitive physiological systems contributes to the development of individual differences in fearful temperament or merely reflects these differences.

Limbic dysregulation is associated with lowered heart rate variability and increased trait anxiety in healthy adults

We tested whether dynamic interaction between limbic regions supports a control systems model of excitatory and inhibitory components of a negative feedback loop, and whether dysregulation of those dynamics might correlate with trait differences in anxiety and their cardiac characteristics among healthy adults. Sixty-five subjects received fMRI scans while passively viewing angry, fearful, happy, and neutral facial stimuli. Subjects also completed a trait anxiety inventory, and were monitored using ambulatory wake ECG. The ECG data were analyzed for heart rate variability, a measure of autonomic regulation. The fMRI data were analyzed with respect to six limbic regions (bilateral amygdala, bilateral hippocampus, Brodmann Areas 9, 45) using limbic time-series cross-correlations, maximum BOLD amplitude, and BOLD amplitude at each point in the time-series. Diminished coupling between limbic time-series in response to the neutral, fearful, and happy faces was associated with greater trait anxiety, greater sympathetic activation, and lowered heart rate variability. Individuals with greater levels of trait anxiety showed delayed activation of Brodmann Area 45 in response to the fearful and happy faces, and lowered Brodmann Area 45 activation with prolonged left amygdala activation in response to the neutral faces. The dynamics support limbic regulation as a control system, in which dysregulation, as assessed by diminished coupling between limbic time-series, is associated with increased trait anxiety and excitatory autonomic outputs. Trait-anxious individuals showed delayed inhibitory activation in response to overt-affect stimuli and diminished inhibitory activation with delayed extinction of excitatory activation in response to ambiguous-affect stimuli.

Autonomic reactivity and clinical severity in children with sickle cell disease

Individual differences in autonomic nervous system reactivity have been studied in relation to physical and mental health outcomes, but rarely among children with chronic disease. The purpose of this study was to examine the associations among autonomic reactivity, clinical severity, family stressors, and mental health symptoms in children with homozygous sickle cell disease. Nineteen children with homozygous sickle cell disease participated in a cross-sectional study involving parent-completed measures, medical record reviews and laboratory-based measures of autonomic nervous system responses to social, cognitive, physical and emotional challenges. Autonomic reactivity was significantly associated with both clinical severity and externalizing behavior symptoms. Children with greater parasympathetic withdrawal during challenges compared to rest had significantly more severe disease (r = -0.45, p < 0.05); greater sympathetic activation during challenges compared to rest was associated with more externalizing behavior symptoms ( r= 0.44, p < 0.05). Children experiencing major family stressors had internalizing behavior symptoms but no difference in autonomic reactivity or clinical severity compared to children experiencing fewer family stressors. Individual differences in autonomic reactivity may offer a new, biologically plausible account for observed variation in painful episodes, other physical complications and behavioral symptoms among children with sickle cell disease.

Effects of selective breeding for infant rat ultrasonic vocalization on cardiac responses to isolation.

Heart rates (HR) and autonomic control of heart period (HP) during maternal separation and isolation were measured at postnatal days (P) 10 and 18 in rat pups selectively bred for high, low, and random rates of infant ultrasonic vocalization. P10 pups displayed no significant line differences in HRs, strong tonic basal sympathetic control of HP and little sympathetic reactivity to isolation, and no evidence of tonic baseline or phasic parasympathetic responses to isolation. At P18, during isolation and recovery, Low HRs were significantly higher compared with Random and High pups. High HRs were significantly higher compared with the Random line in the last third of isolation and through recovery. The higher HRs of Low pups during stress were due to greater parasympathetic withdrawal, but greater sympathetic activation could not be ruled out. Higher HRs in High pups were due to increased sympathetic activation. Thus, increases in HR responses in the selected lines are due to different underlying autonomic processes.

Stressed power motivation, sympathetic activation, immune function, and illness.

Previous research has reported that individuals high in the need for Power, high in inhibition, and high in power stress (the HHH group) are more likely than other individuals to report more severe illnesses. The present study investigates the possibility that the mechanism underlying this relationship is greater sympathetic activation in the HHH group which has an immunosuppressive effect. College males with the HHH syndrome reported more frequent and more severe illnesses than other individuals, as in previous studies. More of the HHH than other subjects also showed above average epinephrine excretion rates in urine and below average concentrations of immunoglobulin A in saliva (S-IgA). Furthermore, higher rates of epinephrine excretion were significantly associated with lower S-IgA concentrations, and lower S-IgA concentrations were significantly associated with reports of more frequent illnesses. The findings are interpreted as consistent with the hypothesis that a strong need for Power, if it is inhibited and stressed, leads to chronic sympathetic overactivity which has an immunosuppressive effect making individuals characterized by this syndrome more susceptible to illness.