Index Of Sympathovagal Balance Research Articles

Relationships between transepidermal water loss, cutaneous microcirculatory function and autonomic nervous activity.

Several studies have shown that a deterioration of skin properties, an impaired cutaneous microcirculatory function and an imbalance of autonomic nervous activity are observed in smokers and in patients with diabetes mellitus or Raynaud's phenomenon. These observations suggest that skin properties are associated with cutaneous microcirculatory function and autonomic nervous activity in pathological conditions. However, there is no published evidence to support the concept that these two functions have any relationship with skin properties even in healthy subjects. To investigate the hypothesis that these properties are related, we conducted a survey of healthy adult subjects to investigate the relationships between cutaneous microcirculatory function and autonomic nervous activity and skin properties. The hydration of the stratum corneum and transepidermal water loss (TEWL) were investigated as skin properties, and the responsiveness of skin blood flow (SkBF) to local warming was examined as an index of cutaneous microcirculatory function in 19 healthy adult male subjects. Electrocardiograms were monitored for 24 h and heart rate variability was analysed considering low-frequency power (LF: 0.04-0.15 Hz), high-frequency power (HF: 0.15-0.40 Hz) and a ratio of low- to high-frequency power (LF/HF) as indices of autonomic nervous activity; HF is an index of parasympathetic activity, whereas LF/HF is an index of sympathovagal balance. The relationships between those indices were then analysed. A moderate negative correlation was found between TEWL and the relative maximum rate of increases in the responsiveness of SkBF on local warming. A moderate positive and a moderate negative correlation were observed between TEWL and LF/HF or HF, respectively. Moreover, a moderate negative and a moderate positive correlation were shown between the responsiveness of SkBF and LF/HF or HF, respectively. The hydration of the stratum corneum showed no correlations with any indices of microcirculation or autonomic nervous activity. These results indicate that skin barrier function, cutaneous microcirculatory function and autonomic nervous activity are mutually associated in healthy adults.

Functional pharmacological characterization of SER100 in cardiovascular health and disease.

SER100 is a selective nociceptin (NOP) receptor agonist with sodium-potassium-sparing aquaretic and anti-natriuretic activity. This study was designed to characterize the functional cardiovascular pharmacology of SER100 in vitro and in vivo, including experimental models of cardiovascular disease. Haemodynamic, ECG parameters and heart rate variability (HRV) were determined using radiotelemetry in healthy, conscious mice. The haemodynamic and vascular effects of SER100 were also evaluated in two models of cardiovascular disease, spontaneously hypertensive rats (SHR) and murine hypoxia-induced pulmonary hypertension (PH). To elucidate mechanisms underlying the pharmacology of SER100, acute blood pressure recordings were performed in anaesthetized mice, and the reactivity of rodent aorta and mesenteric arteries in response to electrical- and agonist-stimulation assessed. SER100 caused NOP receptor-dependent reductions in mean arterial blood pressure and heart rate that were independent of NO. The hypotensive and vasorelaxant actions of SER100 were potentiated in SHR compared with Wistar Kyoto. Moreover, SER100 reduced several indices of disease severity in experimental PH. Analysis of HRV indicated that SER100 decreased the low/high frequency ratio, an indicator of sympatho-vagal balance, and in electrically stimulated mouse mesenteric arteries SER100 inhibited sympathetic-induced contractions. SER100 exerts a chronic hypotensive and bradycardic effects in rodents, including models of systemic and pulmonary hypertension. SER100 produces its cardiovascular effects, at least in part, by inhibition of cardiac and vascular sympathetic activity. SER100 may represent a novel therapeutic candidate in systemic and pulmonary hypertension.

Workload regulation by Sudarshan Kriya: an EEG and ECG perspective

Sudarshan Kriya Yoga (SKY) is a type of rhythmic breathing activity, trivially a form of Pranayama that stimulates physical, mental, emotional, and social well-being. The objective of the present work is to verify the effect of meditation in optimizing task efficiency and regulating stress. It builds on to quantitatively answer if SKY will increase workload tolerance for divided attention tasks in the people sank in it. EEG and ECG recordings were taken from a total of twenty-five subjects who had volunteered for the experiment. Subjects were randomly assigned to two groups of ‘control’ and ‘experimental.’ Their objective scores were collected from the experiment based on NASA’s multi-attribute task battery II and was utilized for workload assessment. Both the groups had no prior experience of SKY. The experimental group was provided with an intervention of SKY for a duration of 30 min everyday. Pre- and post-meditation data were acquired from both groups over a period of 30 and 90 days. It was observed that subjective score of workload (WL) was significantly reduced in the experimental group and performance of the subject increased in terms of task performance. Another astute observation included a considerable increase and decrease in the alpha and beta energies and root mean square of the EEG signal for the experimental group and control group, respectively. In addition to this sympathovagal balance index also decreased in experimental group which indicated reduction in stress. SKY had an effect on stress regulation which in turn enhanced their WL tolerance capacity for a particular multitask activity.

High-fat diet-induced hypertension and autonomic imbalance are associated with an upregulation of CART in the dorsomedial hypothalamus of mice.

We evaluated herein whether diet‐induced obesity alters sympathovagal balance, blood pressure, and neuropeptides levels at the hypothalamus and brainstem of mice. Male C57BL6J mice fed with a high‐fat (HFD) or a high‐fat high‐sucrose (HFHSu), or a regular chow diet (C) for 8 weeks were evaluated for metabolic parameters and blood pressure, the latter being performed in conscious freely moving mice. Spectral analysis from the records of systolic blood pressure (SBP) and cardiac pulse intervals (PI) was performed to analyse the autonomic balance in the cardiovascular system. HFD‐fed mice developed two distinct hemodynamic phenotypes: hypertensive mice (HFD‐H) with high systolic and diastolic BP levels and hypertension‐resistant mice (HFD‐R) whose BP levels were similar to C group. Spectral analysis of SBP and PI variabilities indicate that the low‐frequency (LF)/high‐frequency (HF) ratio, which is an index of sympathovagal balance, is higher in HFD‐H compared to HFD‐R. Along with hypertension and higher LF/HF ratio, HFD‐H mice presented increased hypothalamic mRNA levels of cocaine‐ and amphetamine‐regulated transcript (CART), and increased CART‐positive neurones in the dorsomedial hypothalamus (DMH) by high‐fat diet when compared to C group. Despite developing obesity to similar levels than HFD feeding, intake of a HFHSu was not associated with hypertension in mice neither CART levels increase. Collectively, our main findings indicate that high‐fat diet induced‐hypertension and autonomic imbalance are associated to an upregulation of CART levels in the DMH of mice.

Valsalva maneuver unveils central baroreflex dysfunction with altered blood pressure control in persons with a history of mild traumatic brain injury.

BackgroundPatients with a history of mild TBI (post-mTBI-patients) have an unexplained increase in long-term mortality which might be related to central autonomic dysregulation (CAD). We investigated whether standardized baroreflex-loading, induced by a Valsalva maneuver (VM), unveils CAD in otherwise healthy post-mTBI-patients.MethodsIn 29 healthy persons (31.3 ± 12.2 years; 9 women) and 25 post-mTBI-patients (35.0 ± 13.2 years, 7 women, 4–98 months post-injury), we monitored respiration (RESP), RR-intervals (RRI) and systolic blood pressure (BP) at rest and during three VMs. At rest, we calculated parameters of total autonomic modulation [RRI-coefficient-of-variation (CV), RRI-standard-deviation (RRI-SD), RRI-total-powers], of sympathetic [RRI-low-frequency-powers (LF), BP-LF-powers] and parasympathetic modulation [square-root-of-mean-squared-differences-of-successive-RRIs (RMSSD), RRI-high-frequency-powers (HF)], the index of sympatho-vagal balance (RRI LF/HF-ratios), and baroreflex sensitivity (BRS). We calculated Valsalva-ratios (VR) and times from lowest to highest RRIs after strain (VR-time) as indices of parasympathetic activation, intervals from highest systolic BP-values after strain-release to the time when systolic BP had fallen by 90 % of the differences between peak-phase-IV-BP and baseline-BP (90 %-BP-normalization-times), and velocities of BP-normalization (90 %-BP-normalization-velocities) as indices of sympathetic withdrawal.We compared patient- and control-parameters before and during VM (Mann-Whitney-U-tests or t-tests; significance: P < 0.05).ResultsAt rest, RRI-CVs, RRI-SDs, RRI-total-powers, RRI-LF-powers, BP-LF-powers, RRI-RMSSDs, RRI-HF-powers, and BRS were lower in patients than controls. During VMs, 90 %-BP-normalization-times were longer, and 90 %-BP-normalization-velocities were lower in patients than controls (P < 0.05).ConclusionsReduced autonomic modulation at rest and delayed BP-decrease after VM-induced baroreflex-loading indicate subtle CAD with altered baroreflex adjustment to challenge. More severe autonomic challenge might trigger more prominent cardiovascular dysregulation and thus contribute to increased mortality risk in post-mTBI-patients.

Impaired Autonomic Regulation in Posttraumatic Stress Disorder

Post‐traumatic stress disorder (PTSD) is associated with a significantly increased risk of cardiovascular disease (CVD) and accumulating clinical evidence suggests that autonomic dysregulation due to sympathetic overactivity and/or parasympathetic insufficiency may contribute to progression of CVD in PTSD. Therefore, utilizing a translational approach, we sought to examine autonomic function in both a clinical PTSD population as well as in an animal model of PTSD. In experimental studies, mice were instrumented with radiotelemetry probes to evaluate autonomic indices following Pavlovian fear conditioning. Fear conditioning involves the pairing of a conditioned stimulus (e.g. tone) paired with an aversive uconditioned stimulus (e.g. foot shock) that evokes a conditioned response (e.g. freezing). Twenty‐four hours following fear conditioning, spectral analysis of heart rate was performed and the low‐to high‐frequency ratio (LF:HF) was used as an index of sympathovagal balance. Fear conditioned animals displayed a significant increase in the LF:HF ratio relative to baseline (1.21 ± 0.46; p&lt;0.05) indicating a shift in sympathovagal balance. Two weeks following fear conditioning, we assessed the contribution of sympathetic activity to the maintenance of blood pressure using the ganglionic blocker chlorisondamine (12ug/g i.p.). In response to sympathetic nervous system blockade, fear conditioned animals had a greater fall in blood pressure compared to control (Δ Systolic −71.7± 1.9 vs −39.8 ± 5.8 mmHg; p&lt;0.05). Collectively, these results suggest impairments in autonomic control in an animal model of PTSD prior to the onset of CVD. Finally, these findings will be compared to an ongoing clinical study using a population of combat‐related PTSD (n=13) versus age‐matched controls without PTSD (n=9). Continuous elecrocardiography, beat‐to‐beat arterial blood pressure (BP) measurements, and 24‐hour ambulatory BP measurements have been collected at rest, during, and following mental stress. In an effort to translate our pre‐clinical results, these data will be analyzed for spectral analysis of heart rate variability, BP variability, and 24‐hour ambulatory BP patterns.Support or Funding InformationNIH R00 HL107675‐03 American Heart Association ‐ 15CSA24340001

Comparison between Fast Fourier Transform and Autoregressive Model on Analysis of Autonomic Nervous Function after Food Intake in Women

Purpose: Heart rate variability (HRV) is acknowledged as a useful tool to estimate autonomic function. Fast Fourier transform (FFT) and autoregressive model (AR) are used for power spectral analysis of HRV. However, there is little evidence of agreement between FFT and AR in relation to HRV following food intake in females. In the present study, we applied both FFT and AR after food intake during the follicular and luteal phases, and compared raw low-frequency (LF) and high- frequency (HF) powers, and LF/HF ratio obtained with the two power-spectral analytical methods. Methods: All subjects participated in two sessions: follicular phase session and luteal phase session. In each session, R-R intervals were continuously recorded before and after meals, and power spectral analysis of heart rate variability was performed. We analyzed low-frequency power (LF: 0.04 - 0.15 Hz) and high-frequency power (HF: 0.15 - 0.40 Hz) by using FFT and AR. LF and HF power were computed for each 30 sec, 1 min, 2.5 min, and 5 min of the 5-min R-R data before meal intake and at 20, 40, 60 and 80 min after meal intake. The LF/HF ratio was calculated as an index of sympathovagal balance. Results: In the present study, after 30 sec and 1 min of segment analysis, there was little interchangeability between AR and FFT in LF, HF, and LF/HF ratio in both follicular and luteal phases. In 2.5 min or 5 min of segment analysis, there was interchangeability between FFT and AR in LF and HF, but not in the LF/HF ratio in both follicular and luteal phases. Additionally, FFT underestimated HRV compared with AR, and the extent of underestimation increased with increasing AR value. Conclusion: FFT underestimated HRV compared with AR, and FFT correlated poorly with AR when the analysis segment was shortened.

Effect of Head UP and Head Down Tilt on Heart Rate Variability in Females

Cardiovascular autonomic function can be assesed by the orthostatic stress. This is done mainly by Head Up Tilt (HUT) testing and Head Down Tilt (HDT)Testing. The parameters which represent the cardiovascular autonomic function involved the Heart Rate (HR), Systolic Blood Pressure (SBP), Diastolic Blood Pressure (DBP), Mean Arterial Pressure (MAP) and Pulse Pressure (PP). Heart Rate Variability (HRV) indices provide non-invasive assessment of cardiovascular control mechanisms. Low Frequency (LF) is an indicator of sympathetic system. High Frequency (HF), an index of parasympathetic and the ratio LF/HF is the specific and quantitative index of sympathovagal balance.

Investigation of respiratory and heart rate variability in hypertensive patients

In this paper, in order to examine the effect of respiration on heart rate variability (HRV), signal processing analyses were performed between the signal received from the periodic movement of the chest of respiration and the pulse plethysmograph (PPS) signal, providing the calculation of both the time and frequency behavior of HRV and also including pulse rate information at the same time. Respiration is used as the comparison parameter in both healthy subjects and in hypertensive patients, not only with the time and frequency components of the HRV, but also with the galvanic skin resistance simultaneously taken with body temperature and by calculating these signal changes. In our study, we aim to not only investigate the relationship between hypertension and HRV, but also to investigate the effect of respiration. Hence, in this study, 19 hypertensive patients and 19 healthy controls, who are all women, are used as subjects. As a result of the data received and analyzed from the subjects, HRV both in hypertensive and healthy subjects, the mean value of the high-frequency component and respiratory signal (RSP), and the mean value of the low-frequency/high-frequency ratio accepted as a sympathovagal balance index of the heart rate and RSP are statistically associated.

Automatic stress-relieving music recommendation system based on photoplethysmography-derived heart rate variability analysis.

This paper presents an automatic stress-relieving music recommendation system (ASMRS) for individual music listeners. The ASMRS uses a portable, wireless photoplethysmography module with a finger-type sensor, and a program that translates heartbeat signals from the sensor to the stress index. The sympathovagal balance index (SVI) was calculated from heart rate variability to assess the user's stress levels while listening to music. Twenty-two healthy volunteers participated in the experiment. The results have shown that the participants' SVI values are highly correlated with their prespecified music preferences. The sensitivity and specificity of the favorable music classification also improved as the number of music repetitions increased to 20 times. Based on the SVI values, the system automatically recommends favorable music lists to relieve stress for individuals.

Developmental differences in the effects of alcohol and stress on heart rate variability

Adolescent rats differ in their responses to stress and ethanol from their adult counterparts, although not much is known about the contribution of the autonomic nervous system (ANS) to these differences. This study assessed the impact of stress, ethanol, and their combination on parameters of heart rate variability (HRV) in adolescent and adult male Sprague–Dawley rats. Animals were habituated to the testing box and neck sensors (MouseOX, STARR Life Sciences Corp.) used for recording heart rate (HR). After 8–10min of baseline recording, animals were restrained for 90min or returned home, followed by intraperitoneal injection of 0, 0.5, 1.0, or 1.5g/kg ethanol. The 8–10min test recording occurred 30min post-injection. Ethanol-related decreases in LF (an index of sympathetic activity) were evident under non-stressed conditions in adolescents but only after stress in adults, perhaps in part due to apparent ethanol-induced sympathetic deactivation in adolescents. Parasympathetic tone, indexed by HF, was unaffected by both ethanol and stress in adolescents, while again both the 1.0 and 1.5g/kg ethanol doses decreased HF in adults following stress. Ethanol also decreased low frequency/high frequency tone (LF/HF), an index of sympathovagal balance, only in adolescents, with no decrease evident in adults. Further, stressed adults, and not adolescents, had significantly lower CORT and PROG values than their non-stressed counterparts. Taken together, these results demonstrate notable age differences in the ANS response to ethanol under stressful vs. non-stressful circumstances, reflected by ethanol-mediated autonomic effects that were more pronounced following stressor exposure in adults but under non-stressed conditions in adolescents.

Autonomic dysfunction in mild cognitive impairment: evidence from power spectral analysis of heart rate variability in a cross-sectional case-control study.

BackgroundMild cognitive impairment (MCI) is set to become a major health problem with the exponential ageing of the world's population. The association between MCI and autonomic dysfunction, supported by indirect evidence and rich with clinical implications in terms of progression to dementia and increased risk of mortality and falls, has never been specifically demonstrated.AimTo conduct a comprehensive assessment of autonomic function in subjects with MCI by means of power spectral analysis (PSA) of heart rate variability (HRV) at rest and during provocative manoeuvres.MethodsThis cross-sectional study involved 80 older outpatients (aged ≥65) consecutively referred to a geriatric unit and diagnosed with MCI or normal cognition (controls) based on neuropsychological testing. PSA was performed on 5-minute electrocardiographic recordings under three conditions—supine rest with free breathing (baseline), supine rest with paced breathing at 12 breaths/minute (parasympathetic stimulation), and active standing (orthosympathetic stimulation)—with particular focus on the changes from baseline to stimulation of indices of sympathovagal balance: normalized low frequency (LFn) and high frequency (HFn) powers and the LF/HF ratio. Blood pressure (BP) was measured at baseline and during standing. Given its exploratory nature in a clinical population the study included subjects on medications with a potential to affect HRV.ResultsThere were no significant differences in HRV indices between the two groups at baseline. MCI subjects exhibited smaller physiological changes in all three HRV indices during active standing, consistently with a dysfunction of the orthosympathetic system. Systolic BP after 10 minutes of standing was lower in MCI subjects, suggesting dysautonomia-related orthostatic BP dysregulation.ConclusionsOur study is novel in providing evidence of autonomic dysfunction in MCI. This is associated with orthostatic BP dysregulation and the ongoing follow-up of the study population will determine its prognostic relevance as a predictor of adverse health outcomes.

Wavelet Transform based HRV Analysis

Abstract Heart rate variability (HRV) is a measure of variations of the successive heart beats. It is usually calculated by analyzing the time series of beat-to-beat intervals from ECG signal. HRV is considered as an indicator of the activity of autonomic regulation of circulatory function and as the one of the most significant methods of analyzing the activity of the autonomic nervous system. In this study a Wavelet Packet Transform (WPT) based HRV feature extraction method is presented and compared with the Fourier transformed based one. The results show that a good WPT decomposition gives a significant index of sympathovagal balance, which is the variance (or power) of the ECG signal changes as a function of frequency.

Autonomic dysfunction in reversible cerebral vasoconstriction syndromes

BackgroundAutonomic imbalance may play an important role in the pathogenesis of reversible cerebral vasoconstriction syndromes (RCVS). This study aimed to assess the autonomic function by analyzing heart rate variability (HRV) in patients with RCVS.MethodsPatients with RCVS and age- and gender-matched controls were consecutively recruited. All patients (both ictal and remission stage) and controls underwent 24-hour ambulatory electrocardiographic (ECG) recordings. HRV measures covering time and frequency domains were used to assess autonomic functioning.ResultsThirty-nine patients with RCVS and 39 controls completed the study. Compared to the controls, RCVS patients during the ictal stage showed reductions in parasympathetic-related indices, including the root mean square of difference of consecutive interbeat intervals (RMSSD) (22.1 ± 7.0 vs. 35.2 ± 14.2, p < 0.001), the percentage of adjacent intervals that varied by more than 50 ms (pNN50) (3.7 ± 3.4 vs. 10.6 ± 8.1, p < 0.001), and high-frequency power (HF) (5.82 ± 0.73 vs. 6.77 ± 0.74; p < 0.001), and increased low-frequency/high-frequency (LF/HF) ratio (index of sympathovagal balance) (3.38 ± 1.32 vs. 2.48 ± 1.07; p =0.001). These HRV indices improved partially but remained significantly different from controls during remission.ConclusionsDecreased parasympathetic modulations and accentuated sympathetic activity might be a biological trait in patients with RCVS.

Autonomic functioning in irritable bowel syndrome measured by heart rate variability: A meta‐analysis

To analyze autonomic functioning which presented as the high frequency (HF) component of heart rate variability, a measurement of vagal tone, and the ratio of low frequency (LF) to HF (LF : HF), an indicator of sympathovagal balance in irritable bowel syndrome (IBS) patients. We identified relevant studies by performing a literature search of MEDLINE, EMBASE and the ISI Web of Knowledge to 31 March 2013. Pooled effect sizes with 95% confidence interval (CI) were calculated using a random effects model. Between-study heterogeneity was assessed using the Q test and I(2) statistic. In all, 11 articles including 392 IBS patients and 263 controls met the inclusion criteria of the analysis. IBS patients had lower HF band power (Hedges's g = -0.38, 95% CI -0.68 to -0.09) than the controls (I(2) = 63.6%, P = 0.003). Moreover, IBS patients showed a higher LF : HF (Hedges's g = 0.43, 95% CI 0.13-0.74), with no significant heterogeneity. A subgroup analysis of the HF index according to the recording time yielded different results for the IBS patients and controls. Additionally, constipation-predominant IBS (IBS-C) patients had decreased HF band power, whereas no significant difference was found in LF : HF. Impaired parasympathetic functioning and abnormal sympathovagal balance may be involved in the pathogenesis of IBS. Vagal dysfunction is more obvious in the IBS-C subgroup.

Ontogeny and control of the heart rate power spectrum in the last third of gestation in fetal sheep

Power spectral analysis of fetal heart rate variability has been proposed to provide a non-invasive estimate of autonomic balance. However, there are few systematic data before birth. We therefore examined developmental changes in the frequency power spectrum at very low (0-0.04 Hz), low (0.04-0.15 Hz) and high frequencies (0.15-0.4 Hz), as well as the ratio of low- to high-frequency power (LF/HF), in chronically catheterized, healthy fetal sheep at 0.6 (n = 8), 0.7 (n = 7) and 0.8 gestational age (ga; n = 11). In a second study, 0.8 ga fetuses received either atropine (4.8 mg bolus, then 4.8 mg h(-1) for 30 min, n = 6) or 6-hydroxydopamine (20 mg ml(-1) at 2.5 ml h(-1) for 3 h; n = 9). Data were analysed by sleep state, defined by low-voltage-high-frequency (LV) or high-voltage-low-frequency (HV) EEG. Total spectral power increased with gestational age (P < 0.05), while LF/HF decreased from 0.6 to 0.7 ga. At 0.8 ga, heart rate and LF/HF were significantly higher during HV than LV sleep (P < 0.05). Consistent with this, although total spectral power was not significantly greater during HV sleep, there was a significant interaction between sleep state and frequency band (P = 0.02). Both atropine (P = 0.05) and 6-hydroxydopamine (P < 0.05) were associated with an overall reduction in spectral power but no significant effect on the LF/HF ratio. This study does not support substantial, consistent differences between the frequencies of sympathetic and parasympathetic activity in late-gestation fetal sheep.

Meridian energy analysis of the immediate effect of coffee consumption

IntroductionCoffee consumption has immediate physiological, behavioral, and subjective effects. Despite its widespread use, few studies have described the impact of energy distribution and transformation in meridian vessels. The purpose of this study was to use a Ryodoraku instrument to measure the changes of meridian electrical conductance in healthy volunteers before and after coffee consumption. MethodsIn thirty-one healthy volunteers, the meridian electrical conductance, blood pressure (BP), heart rate (HR), and index of sympathovagal balance were continuously recorded before and after drinking a cup of instant coffee. ResultsStatistical analysis showed that 30min after coffee consumption, the mean values of electrical conductance increased on most meridians except the bilateral Triple Energizer, Liver, and Stomach, as well as the left Kidney and Large Intestine. From 30 to 60 and 60 to 120min, the electrical conductances were maintained significantly only on the bilateral Spleen, Urinary Bladder, and left Pericardium meridians, as well as on the bilateral Spleen, Urinary Bladder, and right Kidney meridians, respectively. The average index of sympathovagal balance decreased significantly at 30min, while BP increased and HR decreased. ConclusionThese findings suggest changes in the specific energy distribution and transformation in the meridian vessels after coffee consumption. Coffee consumption has a similar immediate effect on the cardiovascular system, including increase in BP and decrease in HR. Interestingly, coffee has a temporary stabilizing effect on the higher index of sympathovagal balance. This response may explain why the index is not relevant to the autonomic nervous system but is relevant to mental tasks after coffee consumption.

Gender differences in orthostatic tolerance in the elderly

Gender differences in orthostatic tolerance in the elderly are poorly studied and understood. 48 healthy elderly over 65years (24 women), free from medication and without chronic diseases, were subjected to head-up tilt (HUT) tests: 30° for 10min and 70° for 40min. Blood pressures, stroke volume, total peripheral resistance, blood pressure variability, heart rate variability and baroreceptor sensitivity were measured and test terminations due to vasovagal syncope or unbearable presyncopal symptoms were registered. Mean age was 72; women and men differed in body mass index; 22.2 versus 24.8, respectively (p<0.01). Mean blood pressures were lower among women, with 88 and 98mmHg, respectively (p<0.01) (rest) and 86 and 96mmHg (p<0.01) (tilt 30°). Mean total peripheral resistance index was significantly higher among women during 70° tilt, 13.5 versus 10.8 (p<0.01); no gender differences in heart rate were seen. Women had lower LF/HF ratio (an index of sympathovagal balance) at rest and during 30° tilt (both p<0.05); other heart rate variability measures and baroreceptor sensitivity did not differ. Two women, 9%, and 8 men, 33%, terminated head-up tilt test due to vasovagal syncope or presyncopal symptoms. Gender difference was marginally significant (p=0.05, log-rank test). Higher heart rate at rest (p<0.01) was the only variable significantly associated with the risk of syncope. Our results indicate that elderly men have poorer orthostatic tolerance during protracted postural stress than women of the same age. The underlying reason might be differences in vascular rather than cardiac autonomic control.

Heart rate variability in sciatica patients referred to spine surgery: a case control study

BackgroundA chronic pain condition may result in altered autonomic nervous system regulation in various patient populations. We evaluated whether autonomic regulation differs between sciatica patients referred to spine surgery and age-matched healthy controls analyzed with heart rate variability techniques (HRV).MethodsHRV of patients (n = 201) and healthy controls (n = 138) were measured in standing conditions (5 min). High frequency (HF) power as an index of cardiac vagal modulation and the low-to-high-frequency (LF/HF) ratio and short-term fractal scaling exponent α1 as indices of sympathovagal balance were analyzed. Pain intensity was assessed on a Visual Analog Scale (VAS) and perceived disability with Oswestry Disability Index.ResultsThe Oswestry and VAS scores were higher in the patients than in the controls (p < 0.0001 for both). HF power was markedly lower for the patients compared to the controls (p < 0.0001). The LF/HF ratio and α1 were higher in the patients than in the controls (p < 0.01 for both). After adjusting for sex, smoking, BMI, and leisure-time physical activity, HF power (p = 0.011) and α1 (p = 0.012) still differed between the groups. Among the patients, HF power was slightly associated with the duration of chronic pain (r = −.232, p = 0.003).ConclusionsSciatica patients referred to spine surgery had altered cardiac autonomic regulation expressed as decreased vagal activity and an increased sympathovagal balance toward sympathetic dominance when compared with age-matched healthy controls.

Heart Rate Variability and Electrodermal Activity as Noninvasive Indices of Sympathovagal Balance in Response to Stress

Abstract The autonomic nervous system (ANS) is a principal regulatory system for maintaining homeostasis, adaptability and physiological flexibility of the organism at rest as well as in response to stress. In the aspect of autonomic regulatory inputs on the cardiovascular system, recent research is focused on the study of exaggerated/diminished cardiovascular reactivity in response to mental stress as a risk factor for health complications, e.g. hypertension. Thus, the analysis of biological signals reflecting a physiological shift in sympathovagal balance during stress in the manner of vagal withdrawal associated with sympathetic overactivity is important. The heart rate variability, i.e. “beat-to-beat” oscillations of heart rate around its mean value, reflects mainly complex neurocardiac parasympathetic control. The electrodermal activity could represent “antagonistic” sympathetic activity, the so-called “sympathetic arousal” in response to stress. The detailed study of the physiological parameters under various stressful stimuli and in recovery phase using traditional and novel mathematical analyses could reveal discrete alterations in sympathovagal balance. This article summarizes the importance of heart rate variability and electrodermal activity assessment as the potential noninvasive indices indicating autonomic nervous system activity in response to mental stress.