Heart Rate Variability Domains Research Articles

A systematic review on the effect of high.intensity training on heart rate variability in sports professionals and healthy young adults

BACKGROUND: Exercise plays an essential role in managing cardiovascular disorders, and high-intensity training (HIT) exercise is a potential, time-effective alternative to traditional aerobic exercise. OBJECTIVES: The objective of this study was to evaluate the effect of HIT program on the time and frequency domains of heart rate variability (HRV) in sports professionals and healthy young adults (18–30 years of age) through a systematic review. METHODS: Physiotherapy Evidence Database (PEDro), PubMed, ScienceDirect, Taylor and Francis Online, and Google Scholar were searched for relevant studies. PEDro scale was used to assess internal validity, exclude risk bias, and assess the methodological quality of studies. RESULTS: A total of 4430 search results were obtained by searching for specific keywords, out of which, only 7 studies met the inclusion criteria after removing all the duplicate articles. Our results showed that HIT programs have significant effect on HRV (root mean square of successive difference [RMSSD], mean difference [MD] =13.35, 95% confidence interval [CI] =1.73, 24.97), high-frequency (HF, MD = 381.7, 95% CI = 321.54, 441.86) power, and low- to high-frequency power (MD = -0.10, CI = -0.73, 0.53) ratio in young adult athletes and healthy young adults. No significant difference was found in other HRV variables. CONCLUSION: HIT is an effective exercise program that can cause improvement in parasympathetic and sympathetic cardiac modulation depending on the duration of the HIT program. HIT program can be given for 2–4 weeks to improve HRV in young adults.

Depressed sympathovagal modulation indicates sepsis in patients with suspected infection.

This study explored whether sympathovagal modulation assessed through frequency domains of heart rate variability (HRV) can indicate sepsis in patients with suspected infection.In total, 370 consecutive adult patients with suspected infection admitted to the emergency department were enrolled in this single-center cohort study. A continuous 10-minute electrocardiography for HRV analysis was recorded immediately for these patients after inclusion. Patients were stratified into non-sepsis and sepsis groups based on a sepsis-related organ failure assessment score of ≥2 that met the Third International Consensus Definitions for Sepsis. Seven frequency domains of HRV were compared between these 2 groups.Compared with the non-sepsis group (n = 98), the sepsis group (n = 272) had a significantly lower incidence of respiratory tract infection, higher total power, higher very-low-frequency component, higher high-frequency (HF) component, higher normalized HF component, lower normalized low-frequency (LF) component, and lower LF component/HF component ratio (LF/HF). Multiple logistic regression model identified HF component (odds ratio [OR] = 0.994; 95% confidence interval [CI], 0.990–0.999) and LF/HF (OR = 0.494; 95% CI, 0.423–0.578) as significant variables associated with sepsis. The area under receiver operating characteristic curves of HF component and LF/HF was 0.741 (95% CI, 0.685–0.797) and 0.930 (95% CI, 0.900–0.960), respectively, in identifying sepsis in patients with suspected infection.Tilted sympathovagal balance toward increased vagal activity and depressed sympathetic modulation, assessed by the HF component and LF/HF, may indicate sepsis in patients with suspected infection.

Longitudinal study of the sympathovagal balance in women submitted to bariatric surgery

Studies have shown improvement of the cardiac autonomic balance in post-bariatric patients. Most of these studies included patients using drugs interfering in the autonomic nervous system. This study assessed the time course of changes in the sympathovagal balance after bariatric surgery (Roux-en-Y gastric bypass) in 26 women free from drugs. A 10-min electrocardiographic recording was obtained at baseline and at 3 and 6 months after surgery. Temporal and spectral domains of heart rate variability were analysed. The time domain components of cardiac vagal modulation increased progressively after surgery. In the frequency domain, high frequency power increased from 24.9 at baseline (18.0 to 46.3) to 44.5 at 3 months (23.4 to 65.6), and 54.1 at 6 months after surgery (37.6 to 64.0) (median and IQR in normalized units). Low frequency spectral power decreased from 56.2 at baseline (39.6 to 74.4) to 36.8 at 6 months after surgery (24.9 to 53.9) (P= 0.036). Low frequency/high frequency ratio decreased from 2.3 at baseline (1.0 to 4.2) to 0.8 at 6 months after surgery (0.4 to 1.3) (P= 0.038). Progressive shift towards predominance of vagal tonus was detected in the follow-up. Most of the patients recovered low frequency/high frequency at 6 months after surgery.

Can Heart Rate Variability Determine Recovery Following Distinct Strength Loadings? A Randomized Cross-Over Trial.

This study aimed to compare the acute effects of hypertrophic (HYP) and maximum strength (MAX) loadings on heart rate variability (HRV) and to compare possible loading-specific alterations with other markers of recovery. Ten young men with strength training experience performed two leg press loadings (HYP: five times 10 repetitions at 70% of one repetition maximum (1RM) with 2 minutes inter-set rest; MAX: 15 times one repetition at 100% of 1RM with 3 minutes inter-set rest) in a randomized order. The root mean square of successive differences statistically decreased after both protocols (HYP: 65.7 ± 26.6 ms to 23.9 ± 18.7 ms, p = 0.026; MAX: 77.7 ± 37.0 ms to 55.3 ± 22.3 ms, p = 0.049), while the frequency domains of HRV remained statistically unaltered. The low frequency (LF) band statistically increased at 48h post-MAX only (p = 0.033). Maximal isometric voluntary contraction (MVC) statistically decreased after HYP (p = 0.026) and returned to baseline after 24h of recovery. Creatine kinase (CK) statistically increased above baseline at 1h post-loadings (HYP p = 0.028; MAX p = 0.020), returning to baseline at 24h post. Our findings indicate no distinct associations between changes in HRV and MVC or CK.

P3753Does empagliflozin modulate the autonomic system among patients with type 2 diabetes and coronary artery disease? Insights from the Holter sub-study of the EMPA-Heart CardioLink-6 Randomised Trial

Abstract Introduction The mechanism behind how empagliflozin, a sodium-glucose co-transporter 2 (SGLT2) inhibitor, reduces all-cause and cardiovascular mortality among patients with type 2 diabetes (T2DM) and coronary artery disease (CAD) is unknown. Autonomic tone, as reflected by changes in heart rate variability (HRV), is an established prognosticator in patients with CAD and/or heart failure. Purpose To assess if empagliflozin treatment changes HRV in subjects with T2DM and CAD. Methods In the double-blind EMPA-Heart trial, 97 subjects with T2DM and CAD were randomised to empagliflozin 10 mg/day or placebo for 6 months and underwent 24-hour Holter monitoring at baseline and 6 months. Using automated algorithms, time and frequency HRV domain measures were obtained (standard deviation of NN intervals (SDNN); SD of the average NN intervals for each 5-minute segment (SDANN); root mean square of successive RR interval differences (rMSSD); % interval differences of successive NN intervals >50 ms (pNN50); ratio of low to high frequency (LF/HF)). Changes of these HRV parameters were calculated over 6 months. Between-group differences in HRV parameters were compared using ANCOVA. Results Complete Holter data (baseline and 6-month) were available for 68% (n=66) of the cohort. The average heart rate (HR) at baseline/6 months was 69.5±9.8 bpm/72.8±8.1 bpm and 76±10.4 bpm/76.5±10.6 in the placebo group and empagliflozin group, respectively. Both groups had similar changes in average HR over 6 months. Key Holter data are summarised in the table. SDNN and SDANN were higher in the placebo vs. empagliflozin group at 6 months; no significant difference was noted for all other measures. Empagliflozin 10 mg/day (n=33) Placebo (n=33) Adjusted difference between Empagliflozin and Placebo (ANCOVA) Baseline, Mean (SD) 6-month, Mean (SD) Baseline, Mean (SD) 6-month, Mean (SD) Mean, (95% CI) P-value SDNN (ms) 100.49 (43.74) 98.05 (38.86) 109.35 (30.02) 125.08 (43.83) −18.55 (−34.28, −2.82) 0.022 SDANN (ms) 86.84 (39.34) 83.76 (35.53) 94.70 (28.52) 118.28 (77.41) −20.24 (−37.27, −3.21) 0.021 rMSSD (ms) 27.00 (11.84) 27.22 (13.48) 28.00 (11.58) 27.17 (9.38) −1.23 (−6.02, 3.55) 0.608 pNN50 (%) 7.81 (7.59) 8.32 (9.51) 8.26 (7.8) 6.93 (5.35) 0.51 (−2.61, 3.62) 0.746 LF/HF ratio 1.63 (0.52) 1.65 (0.51) 1.53 (0.43) 1.83 (0.82) −0.08 (−0.38, 0.22) 0.602 Conclusions Among subjects with T2DM and CAD, changes in HRV over 6 months were similar in the empagliflozin and placebo arms suggesting that the mortality benefit conferred by empagliflozin is not associated with positive modulation of autonomic tone. Acknowledgement/Funding This trial was supported by an unrestricted investigator-initiated study grant from Boehringer Ingelheim.

Heart Rate Variability and Risk of All-Cause Death and Cardiovascular Events in Patients With Cardiovascular Disease: A Meta-Analysis of Cohort Studies.

Lower heart rate variability (HRV) is associated with a higher risk of cardiovascular events and mortality, although the extent of the association is uncertain. We performed a meta-analysis of cohort studies to elucidate the association between HRV and the risk of all-cause death or cardiovascular events in patients with cardiovascular disease (CVD) during a follow-up of at least 1 year. We searched four databases (PubMed, MEDLINE, Embase, and Cochrane Central Register of Controlled Trials) and extracted the adjusted hazard ratio (HR) from eligible studies. We included 28 cohort studies involving 3,094 participants in the meta-analysis. Results revealed that lower HRV was associated with a higher risk of all-cause death and cardiovascular events; the pooled HR was 2.27 (95% confidence interval [CI]: 1.72, 3.00) and 1.41 (95% CI: 1.16, 1.72), respectively. In subgroup analyses, the pooled HR of all-cause death was significant for patients with acute myocardial infarction (AMI) but not for those with heart failure. The pooled HR for cardiovascular events was significant for the subgroup of patients with AMI and acute coronary syndrome but not for those with coronary artery disease and heart failure. Additionally, both time and frequency domains of HRV were significantly associated with risk of all-cause death and cardiovascular events in patients with CVD.

Heart Rate Dynamics in Patients with Obstructive Sleep Apnea: Heart Rate Variability and Entropy

Background: Obstructive sleep apnea (OSA), a highly prevalent sleep disorder, is closely related to cardiovascular disease (CVD). Our previous work demonstrated that Shannon entropy of the degree distribution (EDD), obtained from the network domain of heart rate variability (HRV), might be a potential indicator for CVD. Method: To investigate the potential association between OSA and EDD, OSA patients and healthy controls (HCs) were identified from a sleep study database. Then EDD was calculated from electrocardiogram (ECG) signals during sleep, followed by cross-sectional comparisons between OSA patients and HCs, and longitudinal comparisons from baseline to follow-up visits. Furthermore, for OSA patients, the association between EDD and OSA severity, measured by apnea-hypopnea index (AHI), was also analyzed. Results: Compared with HCs, OSA patients had significantly increased EDD during sleep. A positive correlation between EDD and the severity of OSA was also observed. Although the value of EDD became larger with aging, it was not OSA-specified. Conclusion: Increased EDD derived from ECG signals during sleep might be a potential dynamic biomarker to identify OSA patients from HCs, which may be used in screening OSA with high risk before polysomnography is considered.

Correlations between arrhythmogenic substrate and noninvasive risk stratification in ischemic heart disease patients modifications by radiofrequency ablation.

Several noninvasive risk factors for ventricular arrhythmias have been described in postmyocardial infarction (MI) patients, whose relationships with scar characteristics and modifications by ablation are unknown. Twenty-two patients with previous MI referred for ventricular tachycardia ablation were prospectively included. ECG, heart rate variability (HRV), signal-averaged ECG (SA-ECG), and T wave alternans (TWA) were performed before and after radiofrequency ablation. Scar areas were correlated to preablation parameters. Pre and postablation parameters were furthermore compared. Left ventricular ejection fraction and some spectral and time-domain HRV parameters were significantly correlated to the scar areas. QRS duration was larger after vs before ablation (120 ± 29 vs 105 ± 22 msec, P = .01). No significant modification in time or spectral domain of HRV was observed. There was no significant change in TWA and SA-ECG before and after ablation. Borderline decreases in quantitative TWA parameters were noted in patients with positive TWA and successful ablation procedure. Some noninvasive risk factors were linked to the scar areas, but few were significantly modified after ablation. Larger populations are needed to demonstrate significant differences or correlations.

Decreased heart rate variability as a predictor for diabetes-A prospective study of the Brazilian longitudinal study of adult health.

To investigate whether heart rate variability (HRV) is a predictor for the incidence of diabetes in a 4-year follow-up. The HRV of 9192 participants free of diabetes was analysed in time and frequency domains and stratified based on the reference values presented in the literature. The participants were then allocated to one of three groups, according to age-specific value distributions for each HRV domain: lower than the 25th percentile, between the 25th and 75th percentiles, and higher than the 75th percentile. The association between HRV and diabetes incidence at 4-year follow-up was analysed using Poisson regression models with robust estimator. Six hundred thirty-four participants (6.90%) developed diabetes within 4years and five out of six HRV analysed indices showed increased relative risk of developing diabetes associated with low HRV: SDNN (RR=1.29; 95% CI, 1.09-1.52; .003), pNN50 (RR=1.33; 95% CI, 1.11-1.58; .001), RMSSD (RR=1.29; 95% CI, 1.09-1.53; .004), LF (RR=1.25; 95% CI, 1.05-1.48; .012), and HF (RR=1.39; 95% CI, 1.16-1.63; .001). This study suggests that both overall variability and changes in parasympathetic modulation precede the incidence of diabetes. For four HRV indices below the 25th percentile, the risk for incident diabetes was 68% higher than for those participants who presented none. We concluded that HRV is an independent risk predictor of diabetes in a 4-year period.

Does whole body vibration training improve heart rate variability in kidney transplants patients? A randomized clinical trial

BackgroundWhole-body vibration (WBV) is an exercise modality that can promote improvements in heart rate variability (HRV) with lower patient overload, and consequently reduce cardiovascular risk in renal transplant patients. The aim of this study was to evaluate the effects of a 12-week WBV training program of two weekly sessions on HRV. MethodsA double-blind, randomized controlled clinical trial with 12 kidney transplant recipients of both genders who underwent WBV training (35 Hz) twice a week for 12 weeks on alternate days (WBV Group) and training with sub-therapeutic WBV (8 Hz) (Sham Group). Variables were evaluated in time and frequency domains of HRV through the 24-h Holter monitor, heart rate (HR), blood pressure (BP) and maximum oxygen consumption (VO2max) through an exercise stress test. ResultsThe delta between Sham and WBV groups showed an increase in the low frequency (Δ = 959.05 Hz; p = 0.01) and in the high frequency (Δ = 204.42 Hz; p = 0.04) of the HRV compared to Sham group. No changes in the ergometric variables were observed for any of the groups. ConclusionThe present study evidenced an increase in the low and high frequency of HRV in individuals who participated in the Sham WBV group. There was no improvement in the autonomic balance in the groups, in the other HRV parameters, or the exercise test after the WBV training period.

Effects of whole body vibration on cardiac autonomic function and exercise capacity in renal transplant recipients

Background/Aims Whole body vibration is an exercise alternative that can be used in the rehabilitation of renal transplant recipients with the aim of reducing cardiovascular risk. The aim of this study was to evaluate the effects of whole body vibration training on heart rate variability, cardiorespiratory parameters and functional capacity on five renal transplant recipients. Methods Renal transplant recipients underwent whole body vibration exercise twice a week for a total of 12 weeks. All participants were monitored using the 24-hour Holter to evaluate the heart rate variability domains. An exercise test to evaluate maximal oxygen consumption and the distance walked in the Six-Minute Walk Test to evaluate functional capacity were also recorded. Results Overall, two of the five transplant recipients improved sympathovagal balance at the end of the study. Maximal oxygen consumption improved in three transplanted patients, and the distance walked improved for two patients. The results showed that whole body vibration training improved heart rate variability and maximal and submaximal test performance in some transplanted recipients. Conclusion The 12-week training protocol with twice weekly whole body vibration sessions was sufficient to improve heart rate variability and the performance of maximal and submaximal tests in some renal transplant recipients, although the responses were heterogeneous for the considered variables. Whole body vibration may be an alternative to conventional means of physical exercise because it causes minimal cardiovascular stress, which could be especially indicated for this population given the risk presence of arrhythmias and sudden death; therefore studies with better designs need to be developed in order to verify the effectiveness of this intervention.

Association between functional capacity and heart rate variability in patients with uncomplicated type 2 diabetes

Objective: We sought to investigate functional capacity, heart rate variability (HRV), as well as their relationship in the patients with uncomplicated type 2 diabetes.Methods: This cross-sectional observational study included 62 controls and 53 uncomplicated diabetic patients. Included subjects underwent laboratory analysis, 24-h ECG Holter monitoring and cardiopulmonary exercise testing.Results: All parameters of time and frequency domain of HRV were decreased in the diabetic patients. Oxygen uptake at ventilatory threshold (18.3 ± 3.9 vs. 14.6 ± 3.6 mL/kg/min, p < .001), peak oxygen uptake (peak VO2) (27.8 ± 4.1 vs. 19.5 ± 4.3, mL/kg/min, p < .001) and oxygen pulse were significantly lower in the diabetic group, whereas ventilation/carbon dioxide ratio and ventilation/carbon dioxide slope (25.4 ± 2.5 vs. 28.6 ± 3.9, p < .001) were significantly higher in this group. Furthermore, heart rate recovery in the first minute was significantly lower in the diabetic group (26 ± 5 vs. 23 ± 5 beats/min, p = .003). In the whole study population HbA1c and SDNN were independently of other clinical and HRV parameters associated with peak VO2, ventilation/carbon dioxide slope and heart rate recovery in the first minute.Conclusions: Our investigation showed that both functional capacity and HRV were significantly impaired in uncomplicated diabetic patients. HbA1c, an important parameter of glucose regulation, was independently associated with HRV parameters and functional capacity in the whole study population. This reveals a potentially important role of determination of functional capacity and cardiac autonomic function as important markers of preclinical damage in diabetic population.

Comparative effects of amiodarone and dronedarone treatments on cardiac function in a rabbit model.

Aim:The objective of the study was to compare the effects of amiodarone (AM) and dronedarone (DR) on heart rate variability (HRV) and cardiac contractility in a rabbit model.Materials and Methods:A total of 16 male New Zealand white rabbits were divided into two groups, treated either with AM or DR at incremental dosages of 50 mg/kg/day (AM50 and DR50) and 100 mg/kg/day (AM100 and DR100), orally administrated for 7 days. At the end of each period, electrocardiograms were recorded during consciousness and analyzed using the short-term time and frequency domains of HRV. Standard echocardiography and speckle-tracking echocardiography were studied during immobilization with xylazine and ketamine.Results:The results showed that AM100 and DR100 significantly decreased heart rate, total power, low-frequency component, and low-to-high frequency ratio compared with baselines. Most echocardiogram parameters revealed no significant difference from baselines, except for the global circumferential plane strain rate and time to peak standard deviation of strain, which had statistical significances after treating with AM.Conclusion:Both AM and DR possess negative chronotropy and reduce HRV, which may be explained by their sympathetic suppression and calcium channel blocking activities. Theoretically, both antiarrhythmic drugs may also possess negative inotropy, but only AM is shown to have a negative inotropic effect and reduces cardiac dyssynchrony in this model.

Heart rate variability in juvenile systemic lupus erythematosus patients.

Başaran Ö, Çetin İİ, Aydın F, Uncu N, Çakar N, Ekici F, Çelikel Acar B. Heart rate variability in juvenile systemic lupus erythematosus patients. Turk J Pediatr 2019; 61: 733-740. Although neurological involvement has been well recognized in patients with systemic lupus erythematosus (SLE), autonomic nervous system (ANS) involvement has rarely been studied, and has shown conflicting results. The aim of this study was to evaluate the ANS functions by using heart rate variability (HRV) in juvenile patients with SLE. Sixteen juvenile-onset SLE patients and 16 healthy controls were enrolled in the study. All participants underwent 24-hour Holter electrocardiogram monitoring and HRV indices were assessed. The SLE disease activity index (SLEDAI) score was used to assess the disease activity. We analyzed the correlation between disease duration, the SLEDAI score, and the HRV domains. Overall HRV was diminished in patients with SLE compared to controls. There were negative correlations between day and night RMSSD (root-mean-square of the successive normal sinus NN interval differences) and PNN50 (percentage of successive normal sinus NN intervals > 50 ms) values, and SLEDAI (r= -0.588 p=0.017; r= - 0.607 p= 0.013; r= -0.498 p=0.049; r= -0.597 p=0.015, respectively). There were positive correlations between both day and night LF/HF values and SLEDAI (r=0.766 p=0.001; r=0.635 p=0.008, respectively). The results suggest that autonomic dysfunction exists in juvenile patients with SLE. As these children are at increased risk for cardiovascular disease, they need to be assessed for the development of autonomic dysfunction.

The effects of cataract surgery on autonomic heart rate control: a prospective cross-sectional and analytical study

OBJECTIVES:We aimed to evaluate the effects of cataract surgery on cardiac autonomic modulation.METHODS:A cross-sectional and analytical study was conducted at the Hospital Maria Braido in the city of São Caetano do Sul, São Paulo, between 2015 and 2016. We investigated 19 patients of both sexes who were all over 50 years old; all patients had a diagnosis of senile or bilateral cataracts and were recommended to undergo implantation of the intraocular lens. Heart rate variability (HRV) was evaluated before, during and after cataract surgery.RESULTS:There were no significant changes in the time and geometric domains of HRV before, during or after surgery. The high-frequency (HF) band in normalized units (nu) on the spectral analysis significantly increased (p=0.02, Cohen's d=0.9, large effect size). However, the low-frequency (LF) band in nu significantly decreased during surgery (p=0.02, Cohen's d=0.9, large effect size).CONCLUSION:Throughout the intraocular lens implantation cataract surgery, there was an increase in parasympathetic modulation and a decrease in the sympathetic component of the heart rate (HR). We propose that this result is attributable to the supine position of the patients during surgery and the trigeminal reflex.

Autonomic activity and obesity response to driving activity

Background: Driving is one of the hazardous occupations which will lead to stress and strain and lead to heart diseases, and also, the obesity will also known to precipitate most of the cardiovascular diseases. Change in the autonomic nervous system activity will induce and precipitate many cardiovascular diseases. Aims and Objective: Heart rate variability (HRV), a non-invasive technique, is a useful technique used to assess the activity of the autonomic nervous system which will influence the cardiovascular system. Materials and Methods: In this study, we assessed the effect of driving stress on autonomic modulation and obesity, and body mass index (BMI) which is the indicator of the obesity is calculate here. 80 truck drivers were analyzed with time and frequency domains of HRV in normal and deep breathing. Results: Analysis result showed that in time domain HRV significantly decreased as the years of driving increases, but not with the increased BMI. While in low-frequency (LF) component significantly increased and High frequency (HF) component has significantly decreased with the duration of driving exposure, but no such significant changes is seen with the increase of BMI. Conclusion: This result shows that, as the exposure of driving increases, it increases the sympathetic activity and decreases the parasympathetic activity. However, BMI does not affect this group, indicating that the occupational stress is the detrimental factor that may affect the mortality and morbidity due to cardiovascular disease and then obesity.

Heart Rate Variability as a Marker of Changes in Mood State in Daily Life by Photoplethysmography Technique

Introduction: The different mood states in our daily life can affect our mental and emotional health. The aim of our study was to explore photoplethysmography to record heart rate variability as a marker of changes in mood states in our daily life.Materials and Methods: Two groups of affective pictures categorized into positive and negative sets were shown to thirty subjects on two different consecutive days with simultaneously recording of heart rate variability for 5 minutes by photoplethysmography technique. Immediately after recording on each day, 0-9 self-assessment scale was used to assess the mood state of the subject after viewing the set of pictures.Results: Sympathetic domains of heart rate variability like low frequency (200.3 ±4.1 vs. 166.7 ±2.8, p&lt;0.05), low- and high frequency ratio (1.45 ± 0.21 vs. 0.55 ± 0.07, p&lt;0.05) and low frequency (55.8 ± 2.9 vs. 38.6 ± 2.8, p&lt;0.05) significantly increased in negative mood state condition as compared to positive mood state condition. High frequency (157.9 ± 3.9 vs. 264.3 ± 5.3, p&lt;0.05) and high frequency (44 ± 2.9 vs. 61.2 ±4.2, p&lt; 0.05) significantly increased in positive mood state condition as compared to negative mood state condition. There was significant increase in heart rate (78 ± 2.99 vs. 73 ± 3.11, p&lt;0.05) in negative mood state as compared to positive mood state.Conclusions: Increase in sympathetic activity during negative mood state and increase in parasympathetic activity during positive mood state measured by photoplethysmography technique validates this easy and noninvasive mental assessment tool to determine different mood states.

Atrophy of the Vagus Nerve in Parkinson's Disease Revealed by High-Resolution Ultrasonography.

Background: The vagus nerve has been suggested to represent one major route of disease progression in Parkinson's disease (PD). Here, we examined whether patients with idiopathic PD exhibit an atrophy of the vagus nerve in comparison to age-matched controls.Methods: In this cross-sectional study, performed between July 2017 and January 2018, we measured the caliber (cross-sectional area) of the mid-cervical vagus, accessory and phrenic nerves in 20 patients with PD (disease duration: 10.1 ± 7.4 years) and 61 (including 20 age-matched) controls using high-resolution ultrasonography. Ultrasonography and assessments of autonomic function were performed by blinded raters.Results: Mean vagus nerve calibers were lower in patients with PD compared to age-matched controls (right: 0.64 ± 0.17 vs. 1.04 ± 0.20; left: 0.69 ± 0.18 vs. 0.87 ± 0.15 mm2; p < 0.001) while accessory and phrenic nerve calibers did not differ. In controls, age correlated negatively with calibers of the accessory and the phrenic nerve (each p ≤ 0.001), and trended to correlate with vagus nerve caliber (p = 0.023). In patients with PD and age-matched controls combined, the summed caliber of the right and left vagus nerves correlated with the burden of autonomic symptoms on the PD Non-Motor Symptoms Questionnaire (r = −0.46; p = 0.003). Moreover, the caliber of the right but not of the left vagus nerve correlated with the parasympathetic domain of heart rate variability (r = 0.58; p = 0.001).Conclusions: PD is associated with a bilateral atrophy of the vagus nerve but not of the spinal accessory or the phrenic nerves. Our findings suggest that viscero-afferent and viscero-efferent vagal fibers are predominantly affected in PD.

Assessment of Cardiac Autonomic Function in Relation to Methylmercury Neurotoxicity.

After the European Food Safety Authority reviewed reports of methylmercury and heart rate variability (HRV) in 2012, the panel concluded that, although some studies of cardiac autonomy suggested an autonomic effect of methylmercury, the results were inconsistent among studies and the implications for health were unclear. In this study, we reconsider this association by adding a perspective on the physiological context. Cardiovascular rhythmicity is usually studied within different frequency domains of HRV. Three spectral components are usually detected; in humans these are centered at <0.04 Hz, 0.15 Hz (LF), and 0.3 Hz (HF). LF and HF (sympathetic and parasympathetic activities, respectively) are evaluated in terms of frequency and power. By searching PubMed, we identified 13 studies examining the effect of methylmercury exposure on HRV in human populations in the Faroe Islands, the Seychelles and other countries. Considering both reduced HRV and sympathodominant state (i.e., lower HF, higher LF, or higher LF/HF ratio) as autonomic abnormality, eight of them showed the significant association with methylmercury exposure. Five studies failed to demonstrate any significant association. In conclusion, these data suggest that increased methylmercury exposure was consistently associated with autonomic abnormality, though the influence of methylmercury on HRV (e.g., LF) might differ for prenatal and postnatal exposures. The results with HRV should be included in the risk characterization of methylmercury. The HRV parameters calculated by frequency domain analysis appear to be more sensitive to methylmercury exposure than those by time domain analysis.

The effects of physical vibration on heart rate variability as a measure of drowsiness

We investigated the effects of low frequency whole body vibration on heart rate variability (HRV), a measure of autonomic nervous system activation that differentiates between stress and drowsiness. Fifteen participants underwent two simulated driving tasks for 60 min each: one involved whole-body 4–7 Hz vibration delivered through the car seat, and one involved no vibration. The Karolinska Sleepiness Scale (KSS), a subjective measure of drowsiness, demonstrated a significant increase in drowsiness during the task. Within 15–30 min of exposure to vibration, autonomic (sympathetic) activity increased (p < .01) in response to the stress of maintaining alertness and performance when drowsy, and peaked at 60 min (p < .001). Changes in three other HRV domains [higher LF/HF ratios, lower RMSSD (ms) and pNN50 (%) values] were consistent with increased sympathetic activation. These findings have implications for the future development of equivalent drowsiness contours leading to improvements in road safety.Practitioner summary: The effects of physical vibration on driver drowsiness have not been well investigated. This laboratory-controlled study found characteristic changes in heart rate variability (HRV) domains that indicated progressively increasing neurological effort in maintaining alertness in response to low frequency vibration, which becomes significant within 30 min.Abbreviations: ANS: autonomic nervous system; Ctrl: control; EEG: electroencephalography; HF: the power in high frequency range (0.15 Hz-0.4Hz) in the PSD relected parasympathetic activity only; HRV: heart rate variability; KSS: karolinska sleepiness scale; LF: the power in low frequency range (0.04 Hz-0.15Hz) in the PSD reflected both sympathetic and parasympathetic activity of the autonomic nervous system; LF/HF ratio: the ratio of LF to HF indicated the balance between sympathetic and parasympathetic activity; RMSSD: the root mean square of difference of adjacent RR interval; pNN50: the number of successive RR interval pairs that differed by more than 50 ms divided by the total number of RR intervals; RR interval: the differences between successive R-wave occurrence times; PSD: power spectral density; RTP: research training program; SD: standard deviation; SEM: standard error of the Mean; Vib: vibration