Measure Of Sympathovagal Balance Research Articles

Cardiac autonomic modulation in response to postural transition during a virtual reality task in individuals with spinal cord injury: A cross-sectional study.

The postural transition from sitting to standing is a moment of dysautonomic occurrence in individuals with Spinal Cord Injury (SCI). Different tools can be used to minimize this event, such as virtual reality. Thus, we aimed to analyze cardiac autonomic modulation in individuals with SCI during postural transition from the sitting to orthostatism position using a cognitive virtual reality (VR) task. Individuals with and without SCI were positioned on the Easy Stand® device, sitting at rest, at 0° considering the angle between the seat and the floor, elevation at 45°, and orthostatism at 90°, for 5 minutes in each position. Heart rate variability (HRV) measures of sympathovagal balance were collected (heart rate receiver: Polar V800). The groups were subdivided into two groups, one that performed VR as an intervention during the postural angle changes and another group that did not perform VR. We evaluated 76 individuals, 40 with a medical diagnosis of SCI and 36 who composed the able-bodied control group without SCI, matched by age and sex. The HRV results showed that the SCI group who performed the task in VR demonstrated no significant difference in parasympathetic activation and global variability between the sitting versus 90° positions. There was better sympathovagal balance in SCI and able-bodied control groups who performed the VR task between the sitting versus 90° positions. The use of a VR task seems to contribute to better sympathovagal balance, with the potential to reduce dysautonomia during postural changes.

Effects of Physical Training on Heart Rate Variability in Children and Adolescents with Chronic Diseases: A Systematic Review and Meta-analysis.

This study analyzed the effects of physical training programs on heart rate variability, as a measure of sympathovagal balance, in children and adolescents with chronic diseases. Relevant articles were systematically searched in Pubmed, Science Direct, Web of Science, Scopus, Google Scholar and Embase scientific databases. We performed a meta-analysis using an inverse variance heterogeneity model. Effect size calculation was based on the standardized mean differences between pre- and post-intervention assessments, assuring at least a single-group repeated-measures model for each extracted group. Ten studies (252 participants) were included, seven in obese subjects, two in type-1 diabetes, and one in cerebral palsy. When time-domain variables were analyzed, exercise was found to moderately increase RMSSD (SMD=0.478; 95%CI: 0.227 to 0.729; p<0.001), SDNN (SMD=0.367; 95%CI: 0.139 to 0.595; p=0.002) and pNN50 (SMD=0.817; 95%CI: 0.139 to 0.595; p=0.002). As for frequency-domain variables, exercise presented a moderate increasing effect on HF (SMD=0.512; 95%CI: 0.240 to 0.783; p<0.001), a negligible effect for LF (SMD=0.077; 95%CI: -0.259 to 0.412; p<0.001) and a non-significant reduction for LF/HF (SMD=-0.519; 95%CI: -1.162 to 0.124; p=0.114). In conclusion, physical training programs are able to modulate heart rate variability in children and adolescents with chronic diseases, affecting mainly the time-domain variables.

Children with Down syndrome and sleep disordered breathing have altered cardiovascular control.

Sleep disordered breathing (SDB) in typically developing (TD) children is associated with adverse cardiovascular effects. As children with Down syndrome (DS) are at increased risk for SDB, we aimed to compare the cardiovascular effects of SDB in children with DS to those of TD children with and without SDB. Forty-four children with DS (3-19 years) were age and sex matched with 44 TD children without SDB (TD-) and with 44 TD children with matched severity of SDB (TD+). Power spectral density was calculated from ECG recordings, for low frequency (LF), high frequency (HF), total power and the LF/HF ratio. Children with DS had lower HF power, and higher LF/HF during sleep and when awake. There were no differences between groups for LF power. SpO2 nadir, average SpO2 drop and SpO2 > 4% drop were larger in the DS group compared to the TD+ group (p < 0.05 for all). Our findings demonstrate significantly reduced parasympathetic activity (reduced HF power) and increased LF/HF (a measure of sympathovagal balance) in children with DS, together with greater exposure to hypoxia, suggesting SDB has a greater effect in these children that may contribute to an increased risk of adverse cardiovascular outcomes. Sleep disordered breathing in children with Down syndrome exacerbates impaired autonomic control and increases exposure to hypoxia, compared to typically developing children. In typically developing children sleep disordered breathing has adverse effects on autonomic cardiovascular control. The prevalence of sleep disordered breathing is very high in children with Down syndrome; however, studies on the effects on cardiovascular control are limited in this population. This study supports screening and early treatment of sleep disordered breathing in children with Down syndrome.

Socioeconomic Differences in Sympathovagal Balance: The Healthy Life in an Urban Setting Study.

Alterations in sympathovagal balance are associated with cardiovascular disease. If sympathovagal balance differs across socioeconomic groups, it may reflect a mechanism through which disparities in cardiovascular disease occur. We therefore assessed the association between education and occupation with measures of sympathovagal balance in a large multiethnic sample. We included cross-sectional data of 10,202 South Asian Surinamese, African Surinamese, Ghanaian, Turkish, Moroccan, and Dutch-origin participants from the Healthy Life in an Urban Setting study. Sympathovagal balance was measured by baroreflex sensitivity (BRS) and the standard deviation of the interbeat interval, calculated from changes in blood pressure and interbeat intervals, from 5-minute recordings. We calculated geometric means and estimated the relative index of inequality, using age- and ethnicity-adjusted linear regression, to quantify the association between education and occupation and sympathovagal balance. In addition, we assessed whether the association was consistent across ethnic groups. The geometric means of BRS ranged from 8.16 ms/mm Hg (confidence interval [CI] = 7.91-8.43 ms/mm Hg) in low-educated to 14.00 ms/mm Hg (CI = 13.53-14.48 ms/mm Hg) in highly educated women, and from 8.32 ms/mm Hg (CI, 7.97-8.69 ms/mm Hg) in low-educated to 12.25 ms/mm Hg (CI = 11.86-12.66 ms/mm Hg) in highly educated men. High education and occupation were statistically significantly associated with higher BRS and standard deviation of the interbeat interval. Compared with the participants of Dutch origin, a pattern of weaker associations was found in the Surinamese and Ghanaian ethnic groups, but not the Turkish and Moroccan groups. There is a clear socioeconomic gradient in measures of sympathovagal balance, indicating that sympathovagal balance may play a role in socioeconomic disparities in cardiovascular morbidity and mortality.

Effects of central apneas on sympathovagal balance and hemodynamics at night: impact of underlying systolic heart failure

BackgroundIncreased sympathetic drive is the key determinant of systolic heart failure progression, being associated with worse functional status, arrhythmias, and increased mortality. Central sleep apnea is highly prevalent in systolic heart failure, and its effects on sympathovagal balance (SVB) and hemodynamics might depend on relative phase duration and background pathophysiology.ObjectiveThis study compared the effects of central apneas in patients with and without systolic heart failure on SVB and hemodynamics during sleep.MethodsDuring polysomnography, measures of SVB (heart rate and diastolic blood pressure variability) were non-invasively recorded and analyzed along with baroreceptor reflex sensitivity and hemodynamic parameters (stroke volume index, cardiac index, total peripheral resistance index). Data analysis focused on stable non-rapid eye movement N2 sleep, comparing normal breathing with central sleep apnea in subjects with and without systolic heart failure.ResultsTen patients were enrolled per group. In heart failure patients, central apneas had neutral effects on SVB (all p > 0.05 for the high, low, and very low frequency components of heart rate and diastolic blood pressure variability). Patients without heart failure showed an increase in very low and low frequency components of diastolic blood pressure variability in response to central apneas (63 ± 18 vs. 39 ± 9%; p = 0.001, 43 ± 12 vs. 31 ± 15%; p = 0.002). In all patients, central apneas had neutral hemodynamic effects when analyzed over a period of 10 min, but had significant acute hemodynamic effects.ConclusionEffects of central apneas on SVB during sleep depend on underlying systolic heart failure, with neutral effects in heart failure and increased sympathetic drive in idiopathic central apneas.

Presidential Address 2011: Autonomic modes of control and health.

Understanding psychosomatic relations, and their implications for heath, is importantly dependent on our conceptual and measurement models. The historical view of reciprocal control of the autonomic branches is applicable in some contexts, but not others. Control of the autonomic branches can vary reciprocally, independently, and even coactively. Assessment of sympathovagal balance, based on a reciprocal model of regulation of the autonomic branches, may have applications in orthostatic contexts and in insulin resistance in diabetes. However, it does not adequately capture the pattern of autonomic control that is relevant for myocardial infarction (MI; in humans) and experimental cardiac arrest (in mice). A measure of sympathovagal balance (cardiac autonomic balance) was predictive and informative of the autonomic contributions to diabetes but was blind to autonomic contributions to cardiac arrest and its sequelae. However, a metric designed to capture the coactivity dimension of cardiac autonomic regulation (CAR) was predictive of MI and its sequelae. Both human and animal model studies revealed that low CAR (low sympathetic and especially low parasympathetic control) predicted the occurrence of MI and the neuroinflammatory consequences of cardiac arrest. These effects were importantly modulated by social support in both humans and animals, via an apparent oxytocinergic pathway that impacts parasympathetic cardiac control and CAR, and thus neuroinflammation. Results indicate the importance of a physiologically meaningful model of autonomic control in understanding health implications of the modes of autonomic control.

Heart rate variability parameters in children with ventricular preexcitation.

The autonomic nervous system has a regulatory effect on cardiac electrophysiology and arrhythmogenesis. We aimed to assess cardiac autonomic status using heart rate variability (HRV) parameters in children with ventricular preexcitation. The electrocardiography, Holter monitoring, transesophageal electrophysiological study (TEEPS), and invasive electrophysiological study (EPS) results of ventricular preexcitation patients obtained over a 7-year period in our clinic were evaluated. According to the TEEPS results, patients' accessory pathway conduction was classified as adverse (n = 40) or nonadverse (n = 25). The HRV parameters of patients were compared according to tachycardia inducibility that assessed by TEEPS and EPS. Also, HRV parameters were compared in patients with adverse and nonadverse pathway conduction. Further, the HRV parameters of preexcitation patients were compared with those of healthy controls. LF/HF, the best measure of sympathovagal balance, was statistically higher in patients with adverse conduction than in patients without adverse conduction and controls (P=0.001). The LF/HF ratio was higher in ventricular preexcitation patients with inducible tachycardia than those without in EPS (P=0.001). In addition, the LF/HF ratio was higher in symptomatic ventricular preexcitation patients than asymptomatic ones (P=0.001). No difference in HRV parameters was found between preexcitation patients and controls. Autonomic tonus in patients with ventricular preexcitation may affect accessory pathway conduction properties, tachycardia inducibility, and symptomology. The indicator of sympathovagal balance, LF/HF ratio, increased in ventricular preexcitation patients with inducible tachycardia and those that were symptomatic.

Yoga and heart rate variability

Yoga is the union with the divine. Though there are different types of yoga, the primary objective of all yoga practices is to ensure an integral health, free from common health problems and stress‑related disorders. Sympathovagal balance is the cornerstone of a stable homeostasis. Sympathovagal imbalance (SVI) has been reported to be associated with diabetes, hypertension, heart disease and other metabolic disorders. SVI has been documented to promote degeneration and decay and is the basis of all cause morbidity and mortality. Heart rate and heart rate variability (HRV) are measures of sympathovagal balance or imbalance. Resting tachycardia and decreased HRV are established cardiovascular (CV) risks. Practice of yoga, especially relaxation techniques and slow pranayamas has been known to ensure sympathovagal balance, improve HRV and reduce CV risks. In this review, we discuss the types of yoga, physiological basis of improvement of health in yoga practice, the concept and importance of HRV, attainment of sympathovagal balance and improvement of HRV through practice of yoga.

Comparison of the Surgical Pleth Index with autonomic nervous system modulation on cardiac activity during general anaesthesia

Surgical plethysmographic index (SPI) has been proposed as a tool to measure the nociception/antinociception balance during general anaesthesia. Untreated nociception may increase sympathetic tone, but the relationship between SPI and the autonomic nervous system (ANS) is poorly understood. We hypothesised that two different levels of SPI might be associated with differences in ANS modulation, measured by the frequency domain analysis of heart rate variability (HRV). A randomised, cross-over group study, conducted between February and November 2009. University tertiary referral hospital in Milan, Italy. Forty-two adult patients undergoing scheduled laparoscopic abdominal surgery. ECG, noninvasive arterial blood pressure and SPI were recorded during balanced general anaesthesia with inhaled sevoflurane and intravenous remifentanil. After pneumoperitoneum induction, the remifentanil infusion rate was set to obtain two different levels of SPI (>50, HI-SPI, and <50, LO-SPI) for each patient. Arterial pressure, heart rate (HR), low-frequency and high-frequency spectral components, the low frequency/high frequency ratio (measure of sympathovagal balance) and whole power spectrum density of HRV were measured at the two different levels of SPI. Thirty-nine patients were included in the final analysis. During LO-SPI, HR and systolic and mean blood pressures were significantly lower than HI-SPI. The median low frequency/high frequency ratio was reduced during LO-SPI [1.29 interquartile range (IQR) 0.66 to 2.05) vs. 2.36 (1.30 to 3.62), P = 0.008]. The sensitivity analysis revealed a significant correlation between SPI changes and changes of all ANS indices, arterial pressure and HR, with a slightly better correlation for low frequency/high frequency (Spearman ρ = 0.70, IQR 0.484 to 0.834, P < 0.001). In the context of a balanced general anaesthesia in healthy patients undergoing laparoscopic abdominal surgery, ANS modulation seems to correlate with changes in SPI. Further studies are warranted to assess whether this may reflect a change in nociception/antinociception balance or a pharmacodynamic effect of remifentanil.

Assessment of cardiac autonomic function in patients with Duchenne muscular dystrophy using short term heart rate variability measures

BackgroundDuchenne muscular dystrophy (DMD) is a hereditary neuromuscular disorder frequently associated with progressive cardiac dysfunction, and is one of the common causes of death in these children. Early diagnostic markers of cardiac involvement might help in timely intervention. In this study we compared the short term HRV measures of DMD children with that of healthy subjects. MethodOne hundred and twenty-four genetically confirmed boys with DMD and 50 age matched controls were recruited. Error-free, electrocardiogram was recorded in all subjects at rest in the supine position. HRV parameters were computed in time and frequency domains. Time domain measures included standard deviation of NN interval (SDNN), and root of square mean of successive NN interval (RMSSD). Frequency domain consisted of total, low frequency and high frequency power values. Ratio of low frequency and high frequency power values (LF/HF) was determined using customized software. ResultsHRV parameters were significantly altered in DMD children as compared to healthy controls. Following parameters [mean (SD)] were reduced in DMD as compared to controls; RMSSD (in ms) [52.14 (33.2) vs 64.64 (43.2); p = 0.038], High frequency component (nu) [38.77 (14.4) vs 48.02 (17.1); p = 0.001] suggesting a loss of vagal tone. In contrast, measure of sympathovagal balance LF/HF [1.18 (0.87) vs 0.89 (0.79); p = 0.020] was increased in DMD group. ConclusionIn this cross sectional study we have demonstrated alteration in autonomic tone in DMD. Loss of vagal tone and an increase in sympathetic tone were observed in DMD children. Further prospective studies are required to confirm the utility of these measures as predictors of adverse cardiac outcome in DMD.

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.

Evaluation of Autonomic Function in Patients with Sickle Cell Disease in Relation to Nighttime Hypoxemia

Abstract 4764 Background:Sickle cell disease (SCD) is a genetic condition resulting from a homozygous hemoglobin S mutation of the beta globin gene. HbS polymerizes in the deoxygenated state, causing the red cell membrane to become rigid and obstruct blood flow. Ischemia results leading to early organ damage, impaired quality of life and short life expectancy. Patients with SCD die from many causes including infection, splenic sequestration, stroke, and pulmonary emboli, however; a number of deaths in this population are acute and unexplained. The increased risk of sudden death is hypothesized to be associated with autonomic dysfunction. Heart rate variability (HRV) is a measurement of autonomic function and predictor of risk of sudden death. Measures of HRV can be compared to other factors associated with autonomic dysfunction. Individuals with obstructive sleep apnea have increased sympathetic tone. We hypothesized that SCD subjects that experienced nighttime hypoxemia will have autonomic dysfunction. Methods:Subjects were fitted with an ambulatory electrocardiogram device (Acitheart, CamNTech, Inc) and monitored for 24 hours. High frequency power (HFP), a measure of cardiac parasympathetic tone, and low:high ratio (LHR), a measure of sympathovagal balance, were calculated from the HRV by the product software. During sleep, baseline oxyhemoglobin saturation (SpO2) and number of desaturations below 88% was monitored using an ambulatory pulse oximeter (WristOX, Respironics, Inc). Bivariate analysis of the median HFP and LHR values over a 24 hour period were compared to baseline SpO2and number of desaturation events. Sex, age and hematologic values including hemoglobin, CRP and lactate dehydrogenase values were also considered. Results:30 SCD subjects (mean age= 26.1 years+10.96, 36% male) were evaluated. Baseline nighttime SpO2 was 95.5+2.8% with 1 subject with a baseline SpO2 < 90%. Baseline SpO2 did not correlate with HF with R2 = 0.03 but did correlate with LHR with R2 = 0.46. There was a mean number of desaturation events of 16.6+38.3 with 4 subjects greater than 25 desaturation events. The number of desaturation events did not correlate with HF with R2 = 0.027 but did correlate with LHR with R2= 0.63. Stepwise multivariate analysis was performed including the baseline SpO2, number of desaturation events, sex, age and hematologic parameters showed that the number of desaturation events was the best predictor of LHR. Conclusions:SCD subjects that experienced nighttime hypoxemia and increased number of desaturation events during sleep have higher LHR ratios consistent with increased sympathovagal tone. Disclosures:Coates:Novartis: Speakers Bureau; Apopharma: Consultancy. Wood:Ferrokin Biosciences: Consultancy; Shire: Consultancy; Apotex: Consultancy, Honoraria; Novartis: Honoraria, Research Funding.

The influence of transcranial direct current stimulation on cardiac autonomic function in healthy human subjects

Transcranial direct current stimulation (tDCS) of the primary motor cortex is a possible therapy to enhance motor rehabilitation after stroke. The aim of this study is to determine any potential autonomic effects of the tDCS electrode montage conventionally used in stroke therapy. The study was approved by the University of Leeds Ethics Committee and conducted in accordance with the Declaration of Helsinki. tDCS was applied over the primary motor cortex at 1mA with a reference electrode placed on the contralateral supraorbital region in 16 healthy subjects (20–48 years; 7 female, 9 male). Subjects visited the department twice and received active or sham tDCS for 10 minutes. Active tDCS was anodal (n=8) or cathodal (n=8). Heart rate (HR), blood pressure (BP) and respiration were recorded at baseline, during tDCS and recovery. ECG data underwent power spectral analysis to calculate heart rate variability (HRV). HRV did not change significantly (p&gt;0.05) however there was a 32% increase in LF/HF ratio (a measure of sympathovagal balance) during anodal tDCS that continued into recovery reaching 42% above baseline. This indicates a trend towards increased sympathetic activity that was supported by a significant increase in LF power (p=0.048) in the anodal tDCS group. These results suggest further investigation is required before tDCS should be used for stroke therapy. This research is supported by the University of Leeds.

Blunted vagal reactivity predicts stress-precipitated tobacco smoking

Long-term smoking can lead to changes in autonomic function, including decreased vagal tone and altered stress responses. One index of the inability to adapt to stress may be blunted vagal reactivity. Stress is a primary mechanism involved in relapse to smoking, but mechanisms leading to stress-precipitated relapse are not well understood. Using an experimental paradigm of stress-precipitated smoking behavior, we examined whether autonomic reactivity mediates the relationship between stress and smoking. High-frequency heart rate variability (HF-HRV), a putative measure of vagal tone, and the ratio of low-to-high frequency HRV (LF/HF), a measure of sympathovagal balance, were assessed. Using a within-subjects design, 32 nicotine-dependent, 15-h abstinent smokers (a subgroup from McKee et al. (J Psychopharmacol 25(4):490-502, 2011)) were exposed to individualized script-driven imagery of stressful and relaxing scenarios and assessed on the ability to resist smoking and subsequent ad-lib smoking. HRV was monitored throughout each laboratory session (maximum 60min following imagery). As expected, stress and ad-lib smoking additively decreased HF-HRV and increased LF/HF. Blunted stress-induced HF-HRV responses reflecting decreased vagal reactivity were associated with less time to initiate smoking and increased craving relief and reinforcement from smoking. These relationships were specific to HF-HRV following stress as neither baseline HF-HRV, HF-HRV following relaxing imagery, or LF/HF predicted smoking behavior. The current findings are the first to experimentally demonstrate that stress-precipitated decreased vagal reactivity predicts the ability to resist smoking. Findings suggest that strategies that normalize vagal reactivity in early abstinent smokers may lead to improved smoking cessation outcomes.

Cardiovascular Variability During Periodic Leg Movements in Sleep in Children

Periodic leg movements in sleep (PLMS) are episodes of repetitive and stereotypic leg movements occurring during sleep. In adults, research indicates that PLMS affects sleep quality and duration and are associated with a shift to relatively greater sympathetic influence over cardiovascular variables. However, little research has been performed to investigate the effect of PLMS episodes on cardiac autonomic control in children. This study aimed to quantify the effect of PLMS episodes during NREM2 sleep on heart rate variability (HRV) measures of sympathovagal balance in children. Overnight polysomnography data from 20 children (7-12 y) referred for assessment of sleep disordered breathing (SDB) were analyzed retrospectively. Ten children with episodes of PLMS were matched for age and SDB severity with a control group of 10 children without PLMS episodes. The LF/HF ratio was significantly higher in the PLM+ compared with both the PLM- periods from PLMS subjects (P < 0.001) and the periods from the control group (P < 0.001). However, this effect could not be parsimoniously interpreted due to the likelihood that leg movements had a direct effect on the lower frequencies. Analysis of the ratio PLM+ to PLM+ plus PLM- indicated parasympathetic inhibition during periods of periodic leg movement and the onset of individual leg movements were associated with cardiac acceleration followed by a return to pre-movement levels. This study identified vagal inhibition in association with episodes of PLMS in children. Rapid cardiac acceleration occurring concurrently with the onset of individual leg movements also suggested decreased vagal activity associated with the movements.

Sympatho-vagale Balance und kardiale Reaktionen bei standardisierten psychomentalen Belastungen / Sympatho-vagal balance and cardiac response to mental challenge

Based on functional relations between the central autonomic network and cortical areas involved in motivational, attentional, affective, and executive function, autonomic regulation can mediate cognitive performance as well as cardiovascular and psychosomatic diseases. Our objective was to test the predictive value of resting heart rate variability (HRV), a measure of sympatho-vagal balance, with regard to the type and intensity of cardiovascular responses to mental challenge. A total of 248 healthy subjects (85 females, aged 47.3+/-7.6 years; 163 males, aged 47.5+/-6.7 years) were included in the study. All participants underwent standardized psychometric testing (e.g., Stroop's color-word-conflict test). First, we found significant increases of heart rate and sympatho-vagal balance (low frequency/high frequency) and significant decreases of absolute LF- and HF-power in response to mental tasks. Second, there were significant differences in cardiovascular response to mental challenge when clustering our population on the basis of sympatho-vagal balance at rest. We conclude that short-term recordings of HRV can provide health-related information of cardio-vascular response to mental challenge. However, there is no association between sympatho-vagal balance at rest and classical cardiovascular risk factors.

Effect of fentanyl on heart rate variability during spontaneous and paced breathing in healthy volunteers

Many studies have been conducted to assess the effects of fentanyl on the autonomic nervous system (ANS) by heart rate variability (HRV) analysis, but disagreement on the results is still present due to confounding influences introduced by concomitant administration of other drugs or opioid-related transitory respiratory depression. We performed a single-drug controlled-breathing study on healthy volunteers to assess the impact of fentanyl on ANS. HRV as a measure of sympathovagal balance was prospectively analyzed with an autoregressive model in 11 subjects during spontaneous and paced breathing (PB) at 20 breaths/min both before and after fentanyl 1 mcg/kg administration. HRV total power, sympathovagal balance (low-frequency/high-frequency ratio) and normalized spectral powers were considered (LFnu, HFnu). Fentanyl led to a reduction of LFnu (from 55.2+/-23.3 to 43.2+/-24.1, P<0.05) without HFnu increase during PB. A decrease in R-R interval variance (from 3345.6+/-3333.4 to 1806.9+/-1328.6 ms(2), P<0.05) was shown after fentanyl administration during spontaneous but not PB. PB alone decreased the HRV total power and R-R interval variance. Low-dose fentanyl administration in healthy volunteers leads to sympathetic and overall ANS modulation decrease, with a trend toward vagal activation.

Nocturnal hypertension and impaired sympathovagal tone in Turner syndrome

Increased blood pressure (BP), night: day BP ratio, and heart rate is seen in Turner syndrome (TS), and an increased risk of ischaemic heart disease and type 2 diabetes, as well as aortic dilatation and dissection. We hypothesized that altered heart rate variability is present in TS in comparison with controls, and can be influenced by hormonal replacement therapy (HRT). We examined the impact of HRT on sympathovagal control of heart rate variability. Patients (n = 8, aged 29.5 +/- 5.3 years; no treatment or HRT) and controls (n = 8, aged 28.5 +/- 4.2 years; no treatment) were examined by short-term spectral analysis (supine-standing), bedside neuropathy tests, and 24-h ambulatory BP. N-terminal pro-brain natriuretic peptide (BNP), renin, aldosterone and urinary albumin excretion was determined. The interaction between position and status (TS or control) was examined for data from spectral analysis. Low-frequency (LF) power, coefficient of component variation of LF (both measures of sympathetic and vagal activity), and the LF: high-frequency (HF) power ratio (a measure of sympathovagal balance) were diminished in TS compared with controls, especially during standing. Systolic and diastolic night ambulatory BP (both P = 0.03), and systolic and diastolic night: day ratio (P = 0.01; P = 0.004) was increased in TS. During HRT diastolic day (P = 0.05) and 24-h diastolic ambulatory BP (P = 0.08) decreased. N-terminal pro-BNP was elevated in TS. Decreased sympathovagal balance or tone and nocturnal hypertension is present in TS, and N-terminal pro-BNP is elevated. HRT did not modulate the sympathovagal tone, but decreased BP. These changes may be linked to the increased cardiovascular risk and possibly the increased risk of aortic dilatation in TS.

Effects of ultrafine and fine particulate and gaseous air pollution on cardiac autonomic control in subjects with coronary artery disease: The ULTRA study

Previous studies have shown an association between elevated concentrations of particulate air pollution and cardiovascular morbidity and mortality. Therefore, the association between daily variation of ultrafine and fine particulate air pollution and cardiac autonomic control measured as heart rate variability (HRV) was studied in a large multicenter study in Amsterdam, the Netherlands, Erfurt, Germany, and Helsinki, Finland. Elderly subjects (n=37 in Amsterdam, n=47 in both Erfurt and Helsinki) with stable coronary artery disease were followed for 6 months with biweekly clinical visits. During the visits, ambulatory electrocardiogram was recorded during a standardized protocol including a 5-min period of paced breathing. Time and frequency domain analyses of HRV were performed. A statistical model was built for each center separately. The mean 24-h particle number concentration (NC) (1,000/cm(3)) of ultrafine particles (diameter 0.01-0.1 microm) was 17.3 in Amsterdam, 21.1 in Erfurt, and 17.0 in Helsinki. The corresponding values for PM2.5 were 20.0, 23.1, and 12.7 microg/m(3). During paced breathing, ultrafine particles, NO(2), and CO were at lags of 0-2 days consistently and significantly associated with decreased low-to-high frequency ratio (LF/HF), a measure of sympathovagal balance. In a pooled analysis across the centers, LF/HF decreased by 13.5% (95% confidence interval: -20.1%, -7.0%) for each 10,000/cm(3) increase in the NC of ultrafine particles (2-day lag). PM2.5 was associated with reduced HF and increased LF/HF in Helsinki, whereas the opposite was true in Erfurt, and in Amsterdam, there were no clear associations between PM2.5 and HRV. The results suggest that the cardiovascular effects of ambient ultrafine and PM2.5 can differ from each other and that their effect may be modified by the characteristics of the exposed subjects and the sources of PM2.5.

Heart rate variability in emergency department patients with sepsis.

To test the hypothesis that heart rate variability (HRV) can provide an early indication of illness severity among patients presenting to the emergency department (ED) with sepsis. The authors enrolled a convenience sample of 15 ED patients meeting the American College of Chest Physicians/Society of Critical Care Medicine criteria for sepsis. Each patient had continuous Holter monitoring performed in the ED. Acute Physiology and Chronic Health II (APACHE II) and Sequential Organ Failure (SOFA) scores were calculated for the day of presentation. Holter tapes obtained in the ED were analyzed off-line to calculate HRV variables for the 5-minute segment with the least artifact and non-sinus beats. These variables were correlated with APACHE II and SOFA scores. LFnu (normalized low-frequency power), an assessment of the relative sympathetic contribution to overall HRV, was correlated with increased illness severity as calculated using APACHE II (r = -0.67, r(2) = 0.43) and SOFA (r = -0.80, r(2) = 0.64) scores. LF/HF ratio (low-frequency/high-frequency ratio), a measure of sympathovagal balance, was correlated with the SOFA score [r = -0.54 (95% CI = -0.83 to -0.01), r(2) = 0.29]. All five patients who required critical care monitoring or ventilatory support or who died during the first 5 days of their hospitalization had LFnu values below 0.5 and LF/HF ratios less than 1.0. None of the patients with measurements greater than these threshold values died or required these interventions during the five days following admission. A single variable, LFnu, which reflects sympathetic modulation of heart rate, accounted for 40-60% of the variance in illness severity scores among patients presenting to the ED with sepsis. HRV, as reflected in LFnu and the LF/HF ratio and measured with a single brief (5-minute) period of monitoring while in the ED, may provide the emergency physician with a readily available, noninvasive, early marker of illness severity. The threshold effect of LFnu and LF/HF in the prediction of early clinical deterioration was an unexpected finding and should be regarded as hypothesis-generating, pending further study.