A quantitative systematic review of normal values for short-term heart rate variability in healthy adults

Effect of handholding on heart rate variability in both patients with cancer and their family caregivers: a randomized crossover study

BACKGROUND

Many family caregivers of patients with cancer feel guilty about self-care. A meaningful relationship with patients reduces such negative feelings and functions as self-care for family caregivers. Moreover, handholding improves autonomic functions in non-cancer patients. However, the effects of handholding on both patients with cancer and family caregivers remain unknown.

METHODS

We evaluated the effects of handholding on heart rate variability (HRV) in patients with cancer and their family caregivers. This randomized crossover study divided patients with cancer and their family caregivers into two trial groups: Handholding trial (the family caregiver holds the patient's hand for five minutes) and Beside trial (the family caregiver stays beside the patient without holding their hand). The study included 37 pairs of patients with cancer who received treatment in the cancer department of a university hospital in Japan and their family caregivers (n = 74). The primary end-point was the change in HRV before and during the intervention.

RESULTS

The median performance status of the patients was 3. An interaction was observed between trials in the standard deviation of the normal-to-normal interval (SDNN) of HRV for family caregivers (F = 7.669; p = 0.006), and a significant difference in time course was observed between the trials (before p = 0.351; during p = 0.003). No interaction was observed between trials in the SDNN for patients (F = 0.331; p = 0.566). Only a main effect in time course (F = 6.254; p = 0.014) was observed. SDNN increased significantly during the intervention in both trials (Handholding trial: p = 0.002, Beside trial: p = 0.049).

CONCLUSIONS

Handholding improves autonomic functions of family caregivers and may function as self-care for family caregivers.

TRIAL REGISTRATION

UMIN000020557 . Registered on January 15, 2016.

Effects of exercise training on heart rate variability in children and adolescents with pulmonary arterial hypertension: a pilot study

Background

Pulmonary arterial hypertension (PAH) is often associated with cardiac autonomic dysfunction, and heart rate variability (HRV) as marker of cardiac autonomic function is even related to disease severity. Knowledge about the effects of physical activity on HRV is limited in these patients. We aimed to assess whether HRV parameters can be influenced by a supervised exercise training program and whether respective changes are related to levels of activity.

Methods

Six children and adolescents with moderate PAH (3 female, mean age 15.0±4.4 years; mean pulmonary to systemic arterial pressure ratio 0.5±0.2) performed supervised endurance and resistance training for 16 weeks. PAH-specific targeted medication remained unchanged during the study period. HRV was assessed before training and after 16 weeks of training by the use of ECG Move accelerometers. HRV indices included: standard deviation of normal-to-normal (NN) intervals (SDNN), square root of the mean of the sum of the squares of differences between successive NN-intervals (RMSSD), proportion of the number of pairs of successive normal-to-normal intervals that differ by more than 50 ms divided by total number of normal-to-normal interval (pNN50), and the Baevsky stress index (BSI) calculated by the histogram method.

Results

Before and after the training program, SDNN, RMSSD and pNN50 correlated with the level of physical activity. Mean values of SDNN, RMSSD and pNN50 did not change significantly due to the training program. Notably, activity level depending SDNN increased markedly after the exercise program (during activity +12.4%, at rest +6.6% and reclining +8.1%, Hedge's g of 0.28, 0.14 and 0.27, respectively). BSI decreased during activity due to the training program reflecting a reduction of stress level (Hedge's g -0.87 indicating an effect of clinical relevance).

Conclusions

According to the experience of this pilot study a workout program of 16 weeks revealed an activity level dependent effect on parameters of autonomic cardiac function in children and adolescents with PAH. This mechanism might contribute to the positive effects of exercise training in patients with PAH.

Assessment of the Impact of Alcohol Consumption Patterns on Heart Rate Variability by Machine Learning in Healthy Young Adults

Background and Objectives: Autonomic nervous system (ANS) dysfunction is present in early stages of alcohol abuse and increases the likelihood of cardiovascular events. Given the nonlinear pattern of dynamic interaction between sympathetic nervous system (SNS) and para sympathetic nervous system (PNS) and the complex relationship with lifestyle factors, machine learning (ML) algorithms are best suited for analyzing alcohol impact over heart rate variability (HRV), because they allow the analysis of complex interactions between multiple variables. This study aimed to characterize autonomic nervous system dysfunction by analysis of HRV correlated with cardiovascular risk factors in young individuals by using machine learning. Materials and Methods: Total of 142 young adults (28.4 ± 4.34 years) agreed to participate in the study. Alcohol intake and drinking patterns were assessed by the AUDIT (Alcohol Use Disorders Identification Test) questionnaire and the YAI (Yearly Alcohol Intake) index. A short 5-min HRV evaluation was performed. Post-hoc analysis and machine learning algorithms were used to assess the impact of alcohol intake on HRV. Results: Binge drinkers presented slight modification in the frequency domain. Heavy drinkers had significantly lower time-domain values: standard deviation of RR intervals (SDNN) and root mean square of the successive differences (RMSSD), compared to casual and binge drinkers. High frequency (HF) values were significantly lower in heavy drinkers (p = 0.002). The higher low-to-high frequency ratio (LF/HF) that we found in heavy drinkers was interpreted as parasympathetic inhibition. Gradient boosting machine learner regression showed that age and alcohol consumption had the biggest scaled impact on the analyzed HRV parameters, followed by smoking, anxiety, depression, and body mass index. Gender and physical activity had the lowest impact on HRV. Conclusions: In healthy young adults, high alcohol intake has a negative impact on HRV in both time and frequency-domains. In parameters like HRV, where a multitude of risk factors can influence measurements, artificial intelligence algorithms seem to be a viable alternative for correct assessment.

Can Exercise Reduce the Autonomic Dysfunction of Patients With Cancer and Its Survivors? A Systematic Review and Meta-Analysis

Background: Cancer therapies have increased patient survival rates, but side effects such as cardiotoxicity and neurotoxicity can lead to autonomic nervous and cardiovascular system dysfunction. This would result in a decrease in parasympathetic activity and the enhancement of sympathetic activity. Heart rate variability (HRV), which reflects autonomic modulation, is a valuable physiological tool since it correlates with cancer-related fatigue, stress, depression, and mortality in patients with cancer.

Objective: This study aimed to analyze the effects of exercise programs on the autonomic modulation, measured by the HRV of patients with cancer and its survivors.

Methods: The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed, and the quality of the articles was assessed with the Physiotherapy Evidence Database (PEDro) scale. The meta-analysis statistic procedure was performed by using RevMan software version 5.3.

Results: From the 252 articles found, six studies were included in the review involving 272 participants aged 30–75 years. Exercise programs had a mean length of 10.4 ± 4.6 weeks, a frequency of 3 ± 1.4 days/week, and a mean duration of 78 ± 23.9 min. In time-domain HRV measures, exercise may increase in the SD of normal-to-normal intervals [p < 0.00001, with a mean difference (MD) of 12.79 ms from 9.03 to 16.55] and a decreased root mean square of successive R–R interval differences (p = 0.002, with an MD of 13.08 ms from 4.90 to 21.27) in comparison with control groups (CG). The frequency-domain data reveal that the exercise group (EG) improve significantly more than the CGs in low frequency [absolute power: p < 0.0001, with a standardized mean difference (SMD) of 0.97 from 0.61 to 1.34; relative power: p = 0.04, with an MD = −7.70 from −15.4 to −0.36], high-frequency [absolute power: p = 0.001, with a SMD of 1.49 from 0.32 to 2.66; relative power: p = 0.04, with an MD of 8.00 normalized units (n.u.) from 0.20 to 15.80], and low-to-high frequency ratio (p = 0.007 with an MD of −0.32 from −0.55 to −0.09).

Conclusion: Exercise programs could lead to positive effects on the autonomic modulation of patients with cancer and its survivors. More beneficial changes may occur with resistance and endurance workouts. However, due to the low number of interventions performed, further research is needed to substantiate the findings and to provide additional insights regarding the exercise intensity required to increase the autonomic modulation of the patient.

Normative data on cardiovascular autonomic function in Greenlandic Inuit

INTRODUCTION

Diabetes is increasing among Greenlandic Inuit; however, the prevalence of cardiovascular autonomic neuropathy (CAN) is yet unknown. The assessment of CAN requires an ability to differentiate between normal and abnormal. The aim was to establish normative reference data of cardiovascular autonomic function in Greenlandic Inuit.

RESEARCH DESIGN AND METHODS

In this cross-sectional study, cardiovascular autonomic function was evaluated in participants without diabetes during the Greenlandic Population Study 2018 and in the town Qasigiannguit in 2020. Assessment included cardiovascular autonomic reflex tests (CARTs) and power spectral analysis of heart rate variability (HRV). Normative reference limits were estimated by applying piecewise linear quantile regression models at the fifth percentile. Models were adjusted for age and sex.

RESULTS

Based on examinations of 472 participants (61.7% females), normative reference data was established for all outcomes. Mean age was 54 years (SD 13.1). Higher age was inversely associated with all outcomes of CARTs and HRV. A linear fall in cardiovascular autonomic function tended to level off beyond age of 60 or 70 years for supine-to-upright position ratio and low frequency power. However, the number of observations in subjects older than 60 or 70 years was limited, which may have caused a flattening of the curve around that age. No other associations were found.

CONCLUSIONS

The general level of the CARTs and HRV for all age groups is notably lower than in previous studies from other nationalities. We speculate that sociodemographic and cultural aspects of the Greenlandic Inuit population including body mass index, smoking, physical activity and alcohol consumption may have affected the cardiovascular autonomic function.

Changes in vascular function and autonomic balance during the first trimester of pregnancy and its relationship with the new-born weight

This study aimed to evaluate vascular function changes and autonomic balance during the first trimester of pregnancy and its relationship with the new-born weight. This prospective study performed in pregnant (PG) women and after delivery (not pregnant: NPG) evaluated the endothelial function (EF) and arterial stiffness (AS) by a non-invasive method. We evaluated the heart rate variability (HRV), parasympathetic nervous system (PNS), sympathetic nervous system (SNS) indexes by electrocardiogram (5 min) and the urinary nitrite excretion (NOx). PG increased EF and NOx and decreased AS and HRV. PG decreased the PNS index and augmented the SNS index. The new-born weight positively correlated with the PNS index (Pearson's r: 0.4291; p<.05), NOx, HRV and negatively correlated with AS. In summary, in pregnancy, although haemodynamically, the SNS activation plays a compensatory role, the low rates of PNS inhibition are essential to ensure normal foetal growth.Impact StatementWhat is already known on this subject? In pregnancy, there are adaptive physiological changes in the cardiovascular system that include increases of EF and decreases AS with an SNS activation. The study of HRV lets to predict the SNS and PNS balance and how they affect blood pressure and vascular function.What the results of this study add? Although it is known that SNS activation plays a compensatory role in healthy pregnancy, this study adds the critical role of PNS. Early in pregnancy, the low rates of PNS inhibition are essential to ensure normal foetal growth.What the implications are of these findings for clinical practice and/or further research? The present results show a potential predictive value of SNS and PNS activity early in pregnancy. It will provide valuable information not only on the pregnant woman's vascular function but also on the new-born weight.

Gaussian process-based kernel as a diagnostic model for prediction of type 2 diabetes mellitus risk using non-linear heart rate variability features

The main objective of the study was to develop a low-cost, non-invasive diagnostic model for the early prediction of T2DM risk and validation of this model on patients. The model was designed based on the machine learning classification technique using non-linear Heart rate variability (HRV) features. The electrocardiogram of the healthy subjects (n = 35) and T2DM subjects (n = 100) were recorded in the supine position for 15 min, and HRV features were extracted. The significant non-linear HRV features were identified through statistical analysis. It was found that Poincare plot features (SD1 and SD2) can differentiate the T2DM subject data from healthy subject data. Several machine learning classifiers, such as Linear Discriminant Analysis (LDA), Quadratic Discriminant Analysis, Naïve Bayes, and Gaussian Process Classifier (GPC), have classified the data based on the cross-validation approach. A GP classifier was implemented using three kernels, namely radial basis, linear, and polynomial kernel, considering the ability to handle the non-linear data. The classifier performance was evaluated and compared using performance metrics such as accuracy(AC), sensitivity(SN), specificity(SP), precision(PR), F1 score, and area under the receiver operating characteristic curve(AUC). Initially, all non-linear HRV features were selected for classification, but the specificity of the model was the limitation. Thus, only two Poincare plot features were used to design the diagnostic model. Our diagnostic model shows the performance using GPC based linear kernel as AC of 92.59%, SN of 96.07%, SP of 81.81%, PR of 94.23%, F1 score of 0.95, and AUC of 0.89, which are more extensive compared to other classification models. Further, the diagnostic model was deployed on the hardware module. Its performance on unknown/test data was validated on 65 subjects (healthy n = 15 and T2DM n = 50). Considering the desirable performance of the diagnostic model, it can be used as an initial screening test tool for a healthcare practitioner to predict T2DM risk.

Can Reactivity of Heart Rate Variability Be a Potential Biomarker and Monitoring Tool to Promote Healthy Aging? A Systematic Review With Meta-Analyses

Background: Monitoring phasic responses of heart rate variability (HRV) in terms of HRV reactivity [i. e., the absolute change from resting state to on-task (i.e., absolute values of HRV measured during exercise)] might provide useful insights into the individual psychophysiological responses of healthy middle-aged to older adults (HOA) to cognitive and physical exercises. Objectives: To summarize the evidence of phasic HRV responses to cognitive and physical exercises, and to evaluate key moderating factors influencing these responses. Methods: A systematic review with meta-analyses was performed. Publications up to May 2020 of the databases Medline (EBSCO), Embase, Cochrane Library, CINAHL, Psycinfo, Web of Science, Scopus, and Pedro were considered. Controlled clinical trials and observational studies measuring phasic HRV responses to cognitive and/or physical exercises in HOA (≥50 years) were included. Results: The initial search identified 6,828 articles, of which 43 were included into the systematic review. Compared to resting state, vagally-mediated HRV indices were significantly reduced during all types of exercises [Hedge's g = -0.608, 95 % CI (-0.999 to -0.218), p = 0.002] indicating a significant parasympathetic withdrawal compared to rest. The key moderating variables of these responses identified included exercise intensity for physical exercises, and participant characteristics (i.e., level of cognitive functioning, physical fitness), task demands (i.e., task complexity and modality) and the individual responses to these cognitive challenges for cognitive exercises. In particular, higher task demands (task complexity and physical exercise intensity) were related to larger HRV reactivities. Better physical fitness and cognition were associated with lower HRV reactivities. Additionally, HRV reactivity appeared to be sensitive to training-induced cognitive and neural changes. Conclusion: HRV reactivity seems to be a promising biomarker for monitoring internal training load and evaluating neurobiological effects of training interventions. Further research is warranted to evaluate the potential of HRV reactivity as a monitoring parameter to guide cognitive-motor training interventions and/or as a biomarker for cognitive impairment. This may facilitate the early detection of cognitive impairment as well as allow individualized training adaptations that, in turn, support the healthy aging process by optimizing individual exercise dose and progression of cognitive-motor training.

Autonomic Nervous System Dysfunction in Primary Sjögren's Syndrome

Primary Sjögren's syndrome (pSS) is an autoimmune disease which primarily affects the exocrine glands, but can also affect other organs, including the nervous system. Many studies have reported evidence of autonomic nervous system (ANS) dysfunction in pSS which may contribute to a wide range of symptoms and functional burden. Symptoms of ANS dysfunction are common and widespread among patients with pSS and are associated with other features of the disease, particularly fatigue. Accumulating data on the inter-relationship between the ANS and the immune system via the vagus nerve have been reported. Vagus nerve stimulation (VNS) has also been associated with improvement in fatigue in patients with pSS. Taken together, these data suggest that the ANS may be a potential treatment target for pSS, in particularly those with fatigue being a predominant symptom. Future research to dissect the link between the ANS, immune dysregulation and clinical manifestations in pSS and to evaluate the potential of VNS as a therapy for pSS is warranted.

Heart Rate Variability Analyses in Parkinson's Disease: A Systematic Review and Meta-Analysis

Recent evidence suggests that the vagus nerve and autonomic dysfunction play an important role in the pathogenesis of Parkinson's disease. Using heart rate variability analysis, the autonomic modulation of cardiac activity can be investigated. This meta-analysis aims to assess if analysis of heart rate variability may indicate decreased parasympathetic tone in patients with Parkinson's disease. The MEDLINE, EMBASE and Cochrane Central databases were searched on 31 December 2020. Studies were included if they: (1) were published in English, (2) analyzed idiopathic Parkinson's disease and healthy adult controls, and (3) reported at least one frequency- or time-domain heart rate variability analysis parameter, which represents parasympathetic regulation. We included 47 studies with 2772 subjects. Random-effects meta-analyses revealed significantly decreased effect sizes in Parkinson patients for the high-frequency spectral component (HFms²) and the short-term measurement of the root mean square of successive normal-to-normal interval differences (RMSSD). However, heterogeneity was high, and there was evidence for publication bias regarding HFms². There is some evidence that a more advanced disease leads to an impaired parasympathetic regulation. In conclusion, short-term measurement of RMSSD is a reliable parameter to assess parasympathetically impaired cardiac modulation in Parkinson patients. The measurement should be performed with a predefined respiratory rate.

Effectiveness of Mobile Technology in Managing Fatigue: Balert App

The performance of professional tasks with a high cognitive, emotional, and even physiological demand, can cause a state of mental fatigue, which implies attentional alterations, greater errors in the tasks performed and a decrease in personal and work productivity caused by a deterioration of the cognitive control processes. The present study presents a mobile phone application named BAlert that allows monitoring and controlling the body's fatigue processes based on the scores obtained in the Stroop effect and the heart rate variability. A pilot study has been carried out with a sample of 63 adults who have used the application a total of 942 times. The results allow us to classify the subjects, by logistic regression analysis, in their fatigue levels in 74% of the occasions. These results highlight the importance of this mobile application to control work fatigue processes in different possible scenarios (military, health, sports, business, etc.).

Initial Investigation of Athletes’ Electrocardiograms Acquired by Wearable Sensors during the Pre-exercise Phase

Aim:

The aim of this study is to support large-scale prevention programs fighting sport-related sudden cardiac death by providing a set of electrocardiographic features representing a starting point in the development of normal reference values for the pre-exercise phase.

Background:

In people with underlying, often unknown, cardiovascular abnormalities, increased cardiovascular load during exercise can trigger sport-related sudden cardiac death. Prevention remains the only weapon to contrast sport-related sudden cardiac death. So far, no reference values have been proposed for electrocardiograms of athletes acquired with wearable sensors in the pre-exercise phase, consisting of the few minutes immediately before the beginning of the training session.

Objective:

To perform an initial investigation of athletes’ electrocardiograms acquired by wearable sensors during the pre-exercise phase.

Methods:

The analyzed electrocardiograms, acquired through BioHarness 3.0 by Zephyr, belong to 51 athletes (Sport Database and Cycling Database of the Cardiovascular Bioengineering Lab of the Università Politecnica delle Marche, Italy). Preliminary values consist of interquartile ranges of six electrocardiographic features which are heart rate, heart-rate variability, QRS duration, ST level, QT interval, and corrected QT interval.

Results:

For athletes 35 years old or younger, preliminary values were [72;91]bpm, [26;47]ms, [85;104]ms, [-0.08;0.08]mm, [326;364]ms and [378;422]ms, respectively. For athletes older than 35 years old, preliminary values were [71;94]bpm, [16;65]ms, [85;100]ms, [-0.11;0.07]mm, [330;368]ms and [394;414]ms, respectively.

Conclusion:

Availability of preliminary reference values could help identify those athletes who, due to electrocardiographic features out of normal ranges, are more likely to develop cardiac complications that may lead to sport-related sudden cardiac death.

Unclear outcomes of heart rate variability following a concussion: a systematic review

PURPOSE

: To systematically regroup articles that were published since the latest systematic search, but with specific inclusion criteria to help comparison that will offer a focused presentation of methods and results. This will offer a full overview of HRV's behavior at rest and during exercise in adults post-concussion.

METHODS

: The systematic review was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) method. A computer-based systematic search was conducted in December 2019 through the Pubmed, Scopus and SPORTDiscus databases. A manual search was performed through the reference list of all articles retained. The reliability of the systematic search was assured by having the article selection process entirely repeated by a second author.

RESULTS

: The systematic search yielded a total of 15 articles to be further analyzed. Results show impairment of HRV during exercise for individuals with concussion, heterogenous studies with lack of control over confounding factors and only less than half of the results showing a significant difference between individuals with concussion and controls.

CONCLUSION

: Further research should try standardizing HRV measurement protocols that control confounding factors to allow easier comparison between studies and allows the possibility for an eventual meta-analysis.

The streamlined allostatic load index is associated with perceived stress in life - findings from the MIDUS study

The wear and tear of the body caused by stressful events is subject of extensive research and can be measured by the allostatic load index (ALI). The aim of this cross-sectional study was to replicate an ALI-5 score in a population sample in the USA and to compare these findings with the original ALI-10 score. Data from the Midlife in the United States Study (MIDUS) assessed between 2004 and 2016 were used to calculate different ALI risk scores with 5 and 10 variables, respectively. Examinations included anthropometric data, heart rate variability (HRV), and blood and urine samples. Questionnaires assessed information on perceived stress and medical history. Logistic regression models estimated odds ratios (OR) with corresponding 95% confidence intervals (CIs) for the association between ALI indices and perceived stress, controlling for various confounders. Subgroup analysis explored the difference in gender and in three age clusters. Data of 1421 participants (43% male, 50.4 ± 9.3 years) were included in the analysis. Adjusted logistic regression models showed an odds ratio of 1.37 ± 0.19 (CI 1.05, 1.80; p=.022) for the association of ALI-5 with perceived stress. This association was stronger in females (OR = 1.62 ± 0.28, CI 1.15, 2.28; p = .006) and did not significantly differ between age clusters. Results for the original ALI-10 score did not reach significance. The streamlined ALI-5 score seems to be a reliable risk score and is strongly associated with perceived stress in life. Longitudinal studies should further elaborate this association in different samples.Lay summary: Stress from different sources can lead to serious diseases. A short composite index comprising of five medical variables is highly associated with perceived stress. This index is able to serve as an early indicator to detect people who are at risk to develop stress-related diseases.

Opening the Schrödinger Box: Short- and Long-Range Mammalian Heart Rate Variability

Background

The interactions between the autonomic nervous system (ANS), intrinsic systems (e.g., endocrine), and internal pacemaker mechanisms govern short (milliseconds–seconds)- and long (seconds–minutes)-range heart rate variability (HRV). However, there is a debate regarding the identity of the mechanism underlying HRV on each time scale. We aim to design a general method that accurately differentiates between the relative contribution of the ANS and pacemaker mechanisms to HRV in various mammals, without the need for drug perturbations or organ isolation. Additionally, we aim to explore the universality of the relative contribution of the ANS and pacemaker system of different mammals.

Methods

This work explored short- and long-range HRVs using published ECG data from dogs, rabbits, and mice. To isolate the effects of ANS on HRV, ECG segments recorded before and after ANS-blockade were compared.

Results

Differentiation of the ANS from extrinsic and intrinsic pacemaker mechanisms was successfully achieved. In dogs, the internal pacemaker mechanisms were the main contributors to long-range and the ANS to short-range HRV. In rabbits and mice, the ANS and the internal pacemaker mechanisms affected both time scales, and anesthesia changed the relative contribution of the pacemaker mechanism to short- and long-range HRVs. In mice, the extrinsic mechanisms affected long-range HRV, while their effect was negligible in rabbits.

Conclusion

We offer a novel approach to determine the relative contributions of ANS and extrinsic and intrinsic pacemaker mechanisms to HRV and highlight the importance of selecting mammalian research models with HRV mechanisms representative of the target species of interest.

Short-Term Fasting and Ingestion of Caloric Drinks Affect Heartbeat-Evoked Potentials and Autonomic Nervous System Activity in Males

Central nervous systems receive and process information from the internal and external environment to maintain homeostasis. This includes interoceptive awareness of the organism’s nutritional state. Whenever food supply is required, feelings of hunger initiate the search for and the consumption of appropriate amounts of nutrients. How this is physiologically regulated in humans has been subjected to research into interoceptive awareness of body states during fasting and food consumption. However, there is no research on the distinct effects of carbohydrate or protein intake on interoception. Therefore, we aimed to investigate the impact of fasting and consumption of standardized carbohydrate and protein shakes on interoception in a repeated-measures cross-over design in a sample of 37 healthy, normal weight males. As a physiological correlate of interoception, we measured heartbeat-evoked potentials (HEPs), which are suggested to reflect the cortical representation of cardiac signals, during eight-minutes resting state EEG-recordings. After a 16-hour fasting period, the HEP amplitudes were lower over right central and parietal electrodes and increased after ingestion of the nutritional shake. Exploratory analyses indicated that the difference between fasting and satiety was more prominent at carbohydrate compared protein testing days. Correlation analyses with heart rate variability (HRV) suggested that high cardiac sympathetic activity is related to lower HEP amplitudes. Furthermore, cardiac sympathetic activity and stress indices decreased from before to after the intervention, whereas HRV increased. Together, this study shows for the first time that fasting and the intake of a nutritional shake affects cardiac measures of autonomic nervous system functioning and the neural correlates of cardiac interoception. These findings could be relevant for diets and psychosomatic disorders, including eating disorders.

Heart rate variability and chronotype - a systematic review

There is a scarcity of evidence on the association between heart rate variability (HRV) and chronotype, i.e., morningness and eveningness. The aim of this systematic review was to examine the association between chronotype, HRV, mood and stress response. We searched PubMed, Web of Science, Scopus, Cinahl, PsycINFO and Google Scholar for peer-reviewed articles published in English between January 2000 and June 2020. A total of 11 articles met the inclusion criteria and were on study population, assessment of HRV and chronotype, main results and study limitations. Seven of the included studies were experimental and four were crossovers. The sample size varied from 9 to 221 participants, and both females and males were included. HRV was assessed using mostly time-domain and frequency-domain parameters; nonlinear parameters were used in only one study. The most used assessments for measuring chronotype were the Horne-Östberg Morningness-Eveningness Questionnaire (MEQ) and the Munich Chronotype Questionnaire (MCTQ). The results showed that chronotype was associated with HRV, but the study designs were situation-specific, focusing, for example, on the effects of shiftwork, stressful situations, exercise, or sleep deprivation on HRV. In addition, some studies showed that evening types (E-type) performed better during evening or nighttime tasks, whereas morning types (M-type) performed better during morning activities. Specifically, E-types showed decreased HRV and HRV recovery in relation to tasks performed during morning or daytime when compared to M-types. As the findings are somewhat contradictory and include some methodological limitations (e.g., small sample sizes, age groups), it is important for future studies to evaluate the association between chronotype and HRV in a longitudinal setting. In addition, further research is needed to determine how chronotype can be optimally and individually utilized to increase the health and well-being of M-type and E-type individuals.

Exploring Heart Rate Variability as a Biomedical Diagnostic Tool for the Disympathetic Dimension of Eight-Constitution Medicine

Background

Eight-Constitution Medicine (ECM), an extension of Traditional Korean Medicine, divides the population into eight groups based on their physiological characteristics. ECM divides these eight groups into two larger groups based on autonomic reactivity: the Sympathicotonic group and the Vagotonic group (herein referred to as the Disympathetic Dimension). Heart Rate Variability (HRV) is a widely used biomedical tool to assess cardiac autonomic function. This raises the question of the utility of using HRV to correctly diagnose ECM constitutions.

Methods

A systematic literature review was conducted to evaluate the correlation between HRV and constitutions in Korean Constitutional Medicine, including Eight-Constitution Medicine (ECM) and Sasang Constitution Medicine (SCM). The articles were obtained from both English (Scopus, PubMed, EMBASE, ProQuest, and Medline) and Korean databases (NDSL and RISS), in addition to Google Scholar, without date restriction. 20 studies met the inclusion criteria, and data were extracted against three aspects: (1) correlation between HRV and constitution, (2) HRV reporting and interpretation, and (3) extraneous factors that were controlled in the studies.

Results

386 articles were initially identified, which was reduced to n = 20 studies which met the inclusion criteria. Of these, 19 were SCM studies and 1 was an ECM study. Sample sizes varied from 10 to 8498 men and women, with an age range of 10-80 years. SCM studies explored HRV differences by constitution, measuring HRV at resting, with controlled breathing, before and after acupuncture stimulation, and by other interventions. SCM studies reported either no significant differences (HRV at resting or with controlled breathing studies) or conflicting data (HRV with acupuncture stimulation studies). The single ECM study measured HRV at resting and after acupuncture stimulation but reported no significant differences between the two groups of Sympathicotonia and Vagotonia.

Conclusions

Due to inconsistencies in study design, study population, and measures of HRV, there was no consistency in the data to support the use of HRV as a biomedical determinant of ECM constitutions.

Heart Rate Variability in Psychology: A Review of HRV Indices and an Analysis Tutorial

The use of heart rate variability (HRV) in research has been greatly popularized over the past decades due to the ease and affordability of HRV collection, coupled with its clinical relevance and significant relationships with psychophysiological constructs and psychopathological disorders. Despite the wide use of electrocardiograms (ECG) in research and advancements in sensor technology, the analytical approach and steps applied to obtain HRV measures can be seen as complex. Thus, this poses a challenge to users who may not have the adequate background knowledge to obtain the HRV indices reliably. To maximize the impact of HRV-related research and its reproducibility, parallel advances in users' understanding of the indices and the standardization of analysis pipelines in its utility will be crucial. This paper addresses this gap and aims to provide an overview of the most up-to-date and commonly used HRV indices, as well as common research areas in which these indices have proven to be very useful, particularly in psychology. In addition, we also provide a step-by-step guide on how to perform HRV analysis using an integrative neurophysiological toolkit, NeuroKit2.

Four Weeks of Detraining Induced by COVID-19 Reverse Cardiac Improvements from Eight Weeks of Fitness-Dance Training in Older Adults with Mild Cognitive Impairment

Physical training is considered as a low-cost intervention to generate cardioprotective benefits and to promote physical and mental health, while reducing the severity of acute respiratory infection symptoms in older adults. However, lockdown measures during COVID-19 have limited people's opportunity to exercise regularly. The aim of this study was to investigate the effect of eight weeks of Fitness and Dance training, followed by four weeks of COVID-19-induced detraining, on cardiac adaptations and physical performance indicators in older adults with mild cognitive impairment (MCI). Twelve older adults (6 males and 6 females) with MCI (age, 73 ± 4.4 y; body mass, 75.3 ± 6.4 kg; height, 172 ± 8 cm; MMSE score: 24-27) participated in eight weeks of a combined Fitness-Dance training intervention (two sessions/week) followed by four weeks of training cessation induced by COVID-19 lockdowns. Wireless Polar Team Pro and Polar heart rate sensors (H10) were used to monitor covered distance, speed, heart rate (HR min, avg and max), time in HR zone 1 to 5, strenuousness (load score), beat-to-beat interval (max RR and avg RR) and heart rate variability (HRV-RMSSD). One-way ANOVA was used to analyze the data of the three test sessions (T1: first training session, T2: last training session of the eight-week training program, and T3: first training session after the four-week training cessation). Statistical analysis showed that eight weeks of combined Fitness-Dance training induced beneficial cardiac adaptations by decreasing HR (HR min, HR avg and HR max) with p < 0.001, ES = 0.5-0.6 and Δ = -7 to-9 bpm, and increasing HRV related responses (max and avg RR and RMSSD), with p < 0.01 and ES = 0.4. Consequently, participants spent more time in comfortable HR zones (e.g., p < 0.0005; ES = 0.7; Δ = 25% for HR zone 1) and showed reduced strenuousness (p = 0.02, Δ = -15% for load score), despite the higher covered total distance and average speed (p < 0.01; ES = 0.4). However, these changes were reversed after only four weeks of COVID-19 induced detraining, with values of all parameters returning to their baseline levels. In conclusion, eight weeks of combined Fitness-Dance training seems to be an efficient strategy to promote cardioprotective benefits in older adults with MCI. Importantly, to maintain these health benefits, training has to be continued and detraining periods should be reduced. During a pandemic, home-based exercise programs may provide an effective and efficient alternative of physical training.

The validity and reliability of an open source biosensing board to quantify heart rate variability

Background

Heart rate variability (HRV) is a popular tool to quantify autonomic function. However, this typically requires an expensive 3-12 lead electrocardiogram (ECG) and BioAmp system. This investigation sought to determine the validity and reliability of an OpenBCI cyton biosensing board (open source) for accurately quantifying HRV.

New method

A cyton board with a 3-lead ECG was employed to acquire heart rate waveform data, which was processed to obtain HRV within both time- and frequency-domains. The concurrent validity was compared to a simultaneous recording from an industry-standard 3-lead ECG (ADInstruments) (n = 15). The reliability of the cyton board was compared between three days within a 7-day timespan (n = 10). Upright quiet-stance short-term HRV metrics were quantified in time- and frequency-domains.

Results

The two devices displayed excellent limits of agreements (all log mean differences ±0.4) and very high between-device variable associations (all r ² > 0.98). Between the three time points in the same subjects, no differences were noted within time- (all p > 0.71) or frequency-domains (all p > 0.88) across testing points. Finally, all HRV metrics exhibited excellent levels of reliability through high Cronbach's Alpha (all ≥0.916) and intraclass correlation coefficients (all ≥0.930); and small standard error of the measurement (all ≤0.7) and typical error of the measurement (all ≤0.1) metrics.

Comparison with existing methods

The cyton board with 3-lead ECG was compared with an industry-standard ADInstruments ECG during HRV assessments. There were no significant differences between devices with respect to time- and frequency-domains. The cyton board displayed high-levels of between-day reliability and provided values harmonious to previous ECG literature highlighting the applicability for longitudinal studies.

Conclusion

With proper background knowledge regarding ECG principles and a small degree of set-up complexity, an open source cyton board can be created and employed to perform multimodal HRV assessments at a fraction of the cost (~4%) of an industry-standard ECG setup.

Association of Heart Rate Variability With Silent Brain Infarcts in Patients With Atrial Fibrillation

Purpose: Silent brain infarcts (SBI) are frequently detected in patients with atrial fibrillation (AF), but it is unknown whether SBI are linked to autonomic dysfunction. We aimed to explore the association of autonomic dysfunction with SBI in AF patients.

Methods: 1,358 AF patients without prior stroke or TIA underwent brain MRI and 5-min resting ECG. We divided our cohort into AF patients who presented in sinus rhythm (SR-group, n = 816) or AF (AF-group, n = 542). HRV triangular index (HRVI), standard deviation of normal-to-normal intervals, mean heart rate, root mean square root of successive differences of normal-to-normal intervals, 5-min total power and power in the low frequency, high frequency and very low frequency range were calculated. Primary outcome was presence of SBI in the SR group, defined as large non-cortical or cortical infarcts. Secondary outcomes were SBI volumes and topography.

Results: Mean age was 72 ± 9 years, 27% were female. SBI were detected in 10.5% of the SR group and in 19.9% of the AF group (p < 0.001). HRVI <15 was the only HRV parameter associated with the presence of SBI after adjustment for clinical covariates in the SR group [odds ratio (OR) 1.67; 95% confidence interval (CI): 1.03–2.70; p = 0.037]. HRVI <15 was associated with larger brain infarct volumes [β (95% CI) −0.47 (−0.84; −0.09), p = 0.016] in the SR group and was more frequently observed in patients with right- than left-hemispheric SBI (p = 0.017).

Conclusion: Impaired HRVI is associated with SBI in AF patients. AF patients with autonomic dysfunction might undergo systematic brain MRI screening to initiate intensified medical treatment.

Clinical Trials Gov Identifier: NCT02105844.

Recent Advances in Atherosclerotic Disease Screening Using Pervasive Healthcare

Atherosclerosis screening helps the medical model transform from therapeutic medicine to preventive medicine by assessing degree of atherosclerosis prior to the occurrence of fatal vascular events. Pervasive screening emphasizes atherosclerotic monitoring with easy access, quick process, and advanced computing. In this work, we introduced five cutting-edge pervasive technologies including imaging photoplethysmography (iPPG), laser Doppler, radio frequency (RF), thermal imaging (TI), optical fiber sensing and piezoelectric sensor. IPPG measures physiological parameters by using video images that record the subtle skin color changes consistent with cardiac-synchronous blood volume changes in subcutaneous arteries and capillaries. Laser Doppler obtained the information on blood flow by analyzing the spectral components of backscattered light from the illuminated tissues surface. RF is based on Doppler shift caused by the periodic movement of the chest wall induced by respiration and heartbeat. TI measures vital signs by detecting electromagnetic radiation emitted by blood flow. The working principle of optical fiber sensor is to detect the change of light properties caused by the interaction between the measured physiological parameter and the entering light. Piezoelectric sensors are based on the piezoelectric effect of dielectrics. All these pervasive technologies are noninvasive, mobile, and can detect physiological parameters related to atherosclerosis screening.

Different Impact of Heart Rate Variability in the Deep Cerebral and Central Hemodynamics at Rest: An in silico Investigation

Background: Heart rate variability (HRV), defined as the variability between consecutive heartbeats, is a surrogate measure of cardiac vagal tone. It is widely accepted that a decreased HRV is associated to several risk factors and cardiovascular diseases. However, a possible association between HRV and altered cerebral hemodynamics is still debated, suffering from HRV short-term measures and the paucity of high-resolution deep cerebral data. We propose a computational approach to evaluate the deep cerebral and central hemodynamics subject to physiological alterations of HRV in an ideal young healthy patient at rest.

Methods: The cardiovascular-cerebral model is composed by electrical components able to reproduce the response of the different cardiovascular regions and their features. The model was validated over more than thirty studies and recently exploited to understand the hemodynamic mechanisms between cardiac arrythmia and cognitive deficit. Three configurations (baseline, increased HRV, and decreased HRV) are built based on the standard deviation (SDNN) of RR beats. For each configuration, 5,000 RR beats are simulated to investigate the occurrence of extreme values, alteration of the regular hemodynamics pattern, and variation of mean perfusion/pressure levels.

Results: In the cerebral circulation, our results show that HRV has overall a stronger impact on pressure than flow rate mean values but similarly alters pressure and flow rate in terms of extreme events. By comparing reduced and increased HRV, this latter induces a higher probability of altered mean and extreme values, and is therefore more detrimental at distal cerebral level. On the contrary, at central level a decreased HRV induces a higher cardiac effort without improving the mechano-contractile performance, thus overall reducing the heart efficiency.

Conclusions: Present results suggest that: (i) the increase of HRV per se does not seem to be sufficient to trigger a better cerebral hemodynamic response; (ii) by accounting for both central and cerebral circulations, the optimal HRV configuration is found at baseline. Given the relation inversely linking HRV and HR, the presence of this optimal condition can contribute to explain why the mean HR of the general population settles around the baseline value (70 bpm).

Phase contrast coronary blood velocity mapping with both high temporal and spatial resolution using triggered Golden Angle rotated Spiral k-t Sparse Parallel imaging (GASSP) with shifted binning

PURPOSE

High temporal and spatial resolutions are required for coronary blood flow measures. Current spiral breath-hold phase contrast (PC) MRI at 3T focus on either high spatial or high temporal resolution. We propose a golden angle (GA) rotated Spiral k-t Sparse Parallel imaging (GASSP) sequence for both high spatial (0.8 mm) and high temporal (<21 ms) resolutions.

METHODS

GASSP PC data are acquired in left anterior descending and right coronary arteries of eight healthy subjects. Binning of GA rotated spiral data into cardiac frames may lead to large k-space gaps. To reduce those gaps, the binning window is shifted and a triggered GA scheme that resets the rotation angle every heartbeat is proposed. The gap reductions are evaluated in simulations and all subjects. Peak systolic velocity (PSV), peak diastolic velocity (PDV), coronary blood flow rate, and vessel area are validated against two reference scans, and repeatability/reproducibility are determined.

RESULTS

Shifted binning reduced the mean k-space gaps of the triggered GA scheme by 14°-22° in simulations and about 20° in vivo. The k-space gap across three cardiac frames was reduced with the triggered GA scheme compared to the standard GA scheme (35.3°± 3.6° vs. 43°± 13.7°, t-test P = .04). PSV, PDV, flow rate, and area had high intra-scan repeatability (0.92 ≤ intraclass correlation coefficient [ICC] ≤ 0.99), and inter-scan (0.78 ≤ ICC ≤ 0.91) and intra-observer (0.91 ≤ ICC ≤ 0.98) reproducibility.

CONCLUSION

GASSP enables single breath-hold coronary PC MRI with high temporal and spatial resolutions. Shifted binning and a triggered GA scheme reduce k-space gaps. Quantitative coronary flow metrics are highly reproducible, especially within the same scanning session.

Algogen-induced vasosensory reflexes modulate short-term heart rate variability parameters in experimental rat models

OBJECTIVES

The present work was designed to study the modulatory effects of algogen-induced vasosensory reflex responses on short-term heart rate variability (HRV) parameters in naïve and vagotomized rat models.

METHODS

In this study, vasosensory reflex responses were elicited by instilling algogens (bradykinin/histamine), a component of inflammatory mediators into a local segment of medium-sized peripheral blood vessel (femoral artery) while a continuous electrocardiogram (ECG) was recorded. Short-term (5 min) ECG segments obtained from original recordings were examined in detail and relevant data of HRV parameters were pooled. Time domain and frequency domain analyses were performed using dedicated software (LabChart 8, AD Instruments^®, Australia) and results were analyzed.

RESULTS

Bradykinin-induced vasosensory reflexes caused significant alterations in both time domain and frequency domain HRV parameters as compared to the time-matched saline control group. Instillation of bradykinin caused a transient increase in NN interval, RMSSD, TSP, HF power (HFP) along with a decrease in the standard deviation of all normal NN intervals (SDNN), SDNN/RMSSD, LF power (LFP), LFP/HFP. Histamine produced a similar pattern of responses, but HRV alterations were less pronounced compared to those with bradykinin. Further analysis revealed that algogen-induced vasosensory reflex responses caused an increase in the parasympathetic influence on the heart accompanied by a decrease in sympathetic influence. In addition, HRV modulation by algogen-induced vasosensory reflexes was significantly attenuated in vagotomized rats, illustrating the principal role of vagus in the reflex HRV modulation.

CONCLUSIONS

The present study proposes a novel hypothesis regarding the cardio-protective role of inflammatory mediators during acute stress, by potentiating the vagal impact and attenuating the sympathetic impact on the heart.

Time-dependent effects of inspiratory muscle training and detraining on cardiac autonomic control in older women

Inspiratory muscle training improved maximal inspiratory pressure (MIP) and vagal-mediated heart rate variability (HRV) in older women. However, it is unknown what occurs if the training is discontinued (detraining protocol). The aim of this study was to investigate the IMT and detraining effects on resting HRV in older women. Twelve healthy older women (60-72 yrs) enrolled in home-based IMT at 50% MIP (IMT-group) or placebo at 5% MIP (Sham-group) protocol for 4 weeks using a mechanical pressure threshold loading device. The participants were not engaged in any other exercise protocol at that time. During IMT and Sham interventions, the inspiratory load was adjusted weekly by the actual MIP and resting heart rate variability (HRV) evaluated. After training cessation (4 weeks of detraining), participants returned to the lab for HRV and MIP recordings. Adherence to IMT was superior to 95%. IMT increased MIP (23 ± 8 cmH₂O) and vagal-mediated HRV (normalized HF; 37 ± 8%), following by the reduction of sympatho-vagal balance (LF/HF), from the second week to the end of the protocol compared to sham-group. After detraining, IMT-group reduced MIP (-23 ± 8 cmH₂O) and vagal-mediated HRV (normalized HF; -38 ± 14%) returning to baseline values. In conclusion, MIP and vagal-HRV improvements induced by IMT were reversed by four weeks of detraining.

Differential Effects of Sound Intervention and Rest on Cardiovascular Parameters in Cancer Patients: A Randomized Cross-over Trial

Background:

Music therapy or sound interventions were shown to confer beneficial effects in patients with cancer for instance in terms of pain or fear relief and improvement of other patient reported outcomes. Cardiovascular parameters, especially heart rate variability (HRV) were found to have prognostic implications in cancer patients. In this trial we aimed to investigate the effects of a sound intervention on cardiovascular parameters compared to rest in patients with cancer.

Methods and results:

Using a randomized cross-over design, 52 patients (male 13, female 39) with cancer were recruited to receive both a 15-minute sound intervention and a 15-minute rest intervention within 4 weeks with at least a one-week blanking period. Cardiovascular parameters (among others HRV, aortic pulse wave velocity [PWV], augmentation index [Aix], aortic blood pressure [BP], heart rate [HR]) were assessed immediately before (pre) and after (post) the intervention had taken place. HRV (Root mean square of successive RR interval differences [RMSSD, ms]) significantly increased, during sound intervention (median RMSSD pre 24 [range 5-112] vs post 22 [range 9-141], P = .03). Likewise, median PWV, as a direct marker of arterial stiffness, was significantly reduced by sound intervention ([m/s] pre 8.5 [range 5.6-19.6] vs post 8.3 [range 5.6-15.6], P = .04). For both parameters no statistically significant change during rest was observed. HR was lowered by both, rest (P < .0001) and sound intervention (P = .02), with a more pronounced effect by rest. A significant increase in systolic aortic blood pressure was shown by rest ([mmHg] median 101 [range 78-150] vs post median 103 [range 71-152], P = .04) but not during sound intervention (P = .59), while rest intervention led to a decrease in resistance index (pre median 33 [range 13-92] vs post median 32 [11-84], P = .02).

Conclusion:

In comparison with rest, a single sound intervention in patients with cancer improved cardiovascular parameters commonly associated with increased stress levels. Studies with longer follow-up and multiple interventions are warranted.

Trial Registration:

ISRCTN registry 70947363.

Effects of a Short-Term Resistance-Training Program on Heart Rate Variability in Children With Cystic Fibrosis-A Randomized Controlled Trial

Background: Cystic fibrosis (CF) affects the autonomic nervous system (ANS) and exercise in healthy children modulates the interaction between sympathetic and parasympathetic activity. This study aimed to evaluate the effects of a short-term resistance exercise program on heart rate variability (HRV) in children and adolescents with CF.

Methods: A randomized controlled trial was carried out in children diagnosed with CF aged 6–18 years. Individuals were divided into two groups: control (CON) and resistance-training (EX). Individuals in the EX group completed an individualized guided resistance program (5-RM—60–80%) for 8 weeks (3 sessions of 60 min/week). Upper and lower limbs exercises (seated bench press, seated lateral row, and leg press) were used. HRV was measured using a Suunto watch with subjects in lying position.

Results: Nineteen subjects (13 boys) were included (CON = 11; and EX = 8). Mean age was 12.2 ± 3.3, FEV₁ (forced expiratory volume in the first second) z-score was 1.72 ± 1.54 and peak oxygen consumption (VO₂peak) 42.7 ± 7.4 mL.Kg^–1.min^–1. Exercise induced significant changes in the frequency-domain variables, including a decrease in LF power (p = 0.001, d = 0.98) and LF/HF ratio (p = 0.020, d = 0.92), and an increase in HF power (p = 0.001, d = −0.97), compared to the CON group. No significant changes were found for time-domain variables, although increases with a moderate effect size were seen for SDNN (p = 0.152, d = −0.41) and RMSSD (p = 0.059, d = −0.49) compared to the CON group.

Conclusion: A short-term resistance exercise-training program was able to modulate HRV in children and adolescents with CF presenting mild to moderate lung function impairment and good physical condition.

Clinical Trial Registration:www.ClinicalTrials.gov, identifier NCT04293926.

LSD and ketanserin and their impact on the human autonomic nervous system

The interest in lysergic acid diethylamide (LSD) has sparked again due to its supposed positive effects on psychopathological conditions. Yet, most research focuses on the actions of LSD on the central nervous system. The interaction with the autonomic nervous system (ANS) has been neglected so far. Therefore, the aim was to assess the effects of LSD and the serotonin 2A receptor antagonist ketanserin on the ANS as assessed by heart rate variability (HRV) measures and their correlation with subjective drug-induced effects in a randomized, placebo-controlled crossover trial. Thus, ANS activity was derived from electrocardiogram recordings after intake of placebo, LSD or ketanserin, and LSD by calculating R-peak-based measures of sympathetic and parasympathetic activity. Repeated measure ANOVA and partial correlation for HRV measures and subjective experience questionnaires were performed. LSD predominantly increased sympathetic activity, while ketanserin counteracted this effect on the ANS via an increase of parasympathetic tone. Sympathetic activity was positively and parasympathetic activity negatively associated with psychedelic effects of LSD. Furthermore, Placebo HRV measures predicted subjective experiences after LSD intake. The association between trait ANS activity and LSD-induced subjective experiences may serve as a candidate biomarker set for the effectiveness of LSD in the treatment of psychopathological conditions.

Reduction of depressive symptoms during inpatient treatment is not associated with changes in heart rate variability

Vagally mediated heart rate variability (HRV) is a psychophysiological indicator of mental and physical health. Limited research suggests there is reduced vagal activity and resulting lower HRV in patients with Major Depressive Disorder (MDD); however little is actually known about the association between HRV and symptoms of depression and whether the association mirrors symptom improvement following psychotherapy. The aim of this study was to investigate the association between antidepressant therapy, symptom change and HRV in 50 inpatients (68% females; 17–68 years) with a diagnosis of MDD. Severity of depressive symptoms was assessed by self-report (Beck Depression Inventory II) and the Hamilton Rating Scale of Depression. Measures of vagally mediated HRV (root mean square of successive differences and high-frequency) were assessed at multiple measurement points before and after inpatient psychotherapeutic and psychiatric treatment. Results showed an expected negative correlation between HRV and depressive symptoms at intake. Depressive symptoms improved (d = 0.84) without corresponding change in HRV, demonstrating a de-coupling between this psychophysiological indicator and symptom severity. To our knowledge, this study is the first to examine an association between HRV and depressive symptoms before and after psychotherapy. The observed de-coupling of depression and HRV, and its methodological implications for future research are discussed.

Characterization of cardiac autonomic function in COVID-19 using heart rate variability: a hospital based preliminary observational study

OBJECTIVES

The novel corona virus disease, which was initially reported in China in late 2019, has become a global pandemic affecting 330 million cases. COVID-19 affects predominantly the respiratory system, in addition to other organ systems, mainly the cardiovascular system. One of the hypotheses is that virus entering the target cells by binding to angiotensin converting enzyme 2 affecting hypothalamic pituitary axis could lead to dysautonomia which is measured by heart rate variability (HRV). HRV is a non-invasive measure of autonomic function that facilitates identification of COVID-19 patients at the risk of developing cardiovascular complications. So, we aimed to assess HRV in COVID patients and compare between COVID patients and normal controls.

METHODS

In a case control design, we compared 63 COVID-19 infected patients with 43 healthy controls matched for age and gender. Along with clinical characterization, heart rate variability was evaluated using ambulatory 5 min ECG in lead II and expressed in frequency and time domain measures. Statistical analysis was performed using SPSS 17.0.

RESULTS

Mean age of the study population was 49.1 ± 14.2 years and 71 (66.9%) were males. Frequency domain measures high (HF) and low (LF) frequency powers were significantly decreased in COVID-19 patients compared to controls. HF/LF and LF/HF ratios were not different between groups. Time domain measures rMSSD (root mean square of successive RR interval differences) and SDNN (standard deviation of NN intervals) were significantly increased among COVID-19 subjects. COVID-19 infection was associated with increased parasympathetic activity as defined by rMSSD>40 {adjusted odds ratio 7.609 (95% CI 1.61-35.94); p=0.01} and SDNN>60 {adjusted odds ratio 2.620 (95% CI 1.070-6.44); p=0.035} after adjusting for age, gender and comorbidities.

CONCLUSIONS

Our study results showed increased parasympathetic tone in COVID patients. Early diagnosis of autonomic imbalance in COVID patients is needed to plan management and limit progression of disease.

Phasic heart rate variability and the association with cognitive performance: A cross-sectional study in a healthy population setting

Introduction

Sympathovagal balance measured by heart rate variability is a core component of psychophysiological research. Through the close link of physiological and psychological aspects, often a reduced heart rate variability is associated with impaired cognitive function. A better understanding of the associations between cognitive and cardiovascular dysfunctions is necessary to prevent the manifestation of diseases. Therefore, this study investigated phasic heart rate variability using rest, anticipatory, stress, and recovery periods and the association with high and low cognitive performance in a generally healthy population setting.

Methods

114 healthy individuals (40 males, 74 females) aged 20 to 70 participated in the cross-sectional study. The heart rate variability based on standard deviation of NN intervals (SDNN), and the root means square of successive differences (RMSSD), low frequency (LF), high frequency (HF) and LF/HF ratio and its association with high and low cognitive performance measured by the California Verbal Learning Task II were examined.

Results

The results of this study indicate that the paradigm was successful in producing stress and showed a significant association between phasic heart rate variability (SDNN) and verbal episodic memory performance, irrespective of age and sex.

Discussion

The results of this study suggest that a reduced heart rate variability is associated with reduced cognitive function regardless of age and sex and seem to be an early indicator of sympathovagal disbalance.

Conclusion

This leads to the conclusion that differences between high and low cognitive performance might show differences in heart rate variability at an early stage, where no diseases are yet manifest.

Hypoxic Respiratory Chemoreflex Control in Young Trained Swimmers

During an apnea, changes in PaO₂ activate peripheral chemoreceptors to increase respiratory drive. Athletes with continuous apnea, such as breath-hold divers, have shown a decrease in hypoxic ventilatory response (HVR), which could explain the long apnea times; however, this has not been studied in swimmers. We hypothesize that the long periods of voluntary apnea in swimmers is related to a decreased HVR. Therefore, we sought to determine the HVR and cardiovascular adjustments during a maximum voluntary apnea in young-trained swimmers. In fifteen trained swimmers and twenty-seven controls we studied minute ventilation (V_E), arterial saturation (SpO₂), heart rate (HR), and autonomic response [through heart rate variability (HRV) analysis], during acute chemoreflex activation (five inhalations of pure N₂) and maximum voluntary apnea test. In apnea tests, the maximum voluntary apnea time and the end-apnea HR were higher in swimmers than in controls (p < 0.05), as well as a higher low frequency component of HRV (p < 0.05), than controls. Swimmers showed lower HVR than controls (p < 0.01) without differences in cardiac hypoxic response (CHR). We conclude that swimmers had a reduced HVR response and greater maximal voluntary apnea duration, probably due to decreased HVR.

HRVCam: robust camera-based measurement of heart rate variability

SIGNIFICANCE

Non-contact, camera-based heart rate variability estimation is desirable in numerous applications, including medical, automotive, and entertainment. Unfortunately, camera-based HRV accuracy and reliability suffer due to two challenges: (a) darker skin tones result in lower SNR and (b) relative motion induces measurement artifacts.

AIM

We propose an algorithm HRVCam that provides sufficient robustness to low SNR and motion-induced artifacts commonly present in imaging photoplethysmography (iPPG) signals.

APPROACH

HRVCam computes camera-based HRV from the instantaneous frequency of the iPPG signal. HRVCam uses automatic adaptive bandwidth filtering along with discrete energy separation to estimate the instantaneous frequency. The parameters of HRVCam use the observed characteristics of HRV and iPPG signals.

RESULTS

We capture a new dataset containing 16 participants with diverse skin tones. We demonstrate that HRVCam reduces the error in camera-based HRV metrics significantly (more than 50% reduction) for videos with dark skin and face motion.

CONCLUSION

HRVCam can be used on top of iPPG estimation algorithms to provide robust HRV measurements making camera-based HRV practical.

Z-score neurofeedback, heart rate variability biofeedback, and brain coaching for older adults with memory concerns

BACKGROUND

The three-month, multi-domain Memory Boot Camp program incorporates z-score neurofeedback (NFB), heart rate variability (HRV) biofeedback, and one-on-one coaching to teach memory skills and encourage behavior change in diet, sleep, physical fitness, and stress reduction.

OBJECTIVE

This prospective trial evaluates the Memory Boot Camp program for adults ages 55 to 85 with symptoms of Mild Cognitive Impairment (MCI) and subjective memory complaints.

METHODS

Participants were evaluated via the Montreal Cognitive Assessment (MoCA), NeuroTrax Global Cognitive Score, measures of anxiety, depression, sleep, quality of life, quantitative electroencephalography (QEEG), and HRV parameters at four timepoints: baseline, pre-program, post-program, and follow-up. The trial included a three-month waiting period between baseline and pre-program, such that each participant acted as their own control, and follow-up took place six months after completion of the program.

RESULTS

Participants' MoCA scores and self-reported measures of anxiety, depression, sleep quality, and quality of life improved after treatment, and these changes were maintained at follow-up. Physiological changes in HRV parameters after treatment were not significant, however, breathing rate and QEEG parameters were improved at post-program and maintained at follow-up. Finally, participants' improvement in MoCA score over the treatment period was correlated with their improvement in two brain oscillation parameters targeted by the z-score NFB protocol: relative power of delta and relative power of theta.

CONCLUSIONS

Trial results suggest that the Memory Boot Camp program is a promising treatment strategy for older adults with symptoms of MCI and subjective memory complaints.

Maternal Mental Health and Parenting Stress and Their Relationships to Characteristics of the Child With Fragile X Syndrome

Although previous research supports the notion that characteristics of both the child and the mother impact maternal well-being and parenting stress in mothers of children with FXS, more work is needed in which self-report measures are supplemented by physiological measures of stress and well-being. The inclusion of physiological measures, such as heart rate variability (HRV), may provide a window into the biological origins and consequences of maternal perceptions of their experiences, including the challenges of raising a child with developmental challenges. The proposed project, therefore, involved the collection of multimodal assessment data from mothers and their school-aged children with FXS. Further, given the importance of understanding how mothers of youth with FXS are faring in their everyday environment, the present study collected all data using telehealth procedures and wearable technology. Participants were 20 biological mothers and their children with FXS between the ages of 6 and 11 years. We measured maternal mental health and parenting stress through self-report as well as through HRV as a more objective measure of psychological well-being. We also examined the associations between these variables and child characteristics such as externalizing and internalizing behaviors as well as autism symptomatology. We found significant support for an elevated rate of depressive symptoms in the sample of mothers (35%) and some potential indicators for heightened rates of anxiety (15%) when compared to normed samples and rates in the general population. We also found that the mothers presented with an atypical HRV profile akin to those experiencing depression or chronic stress, although limitations of the present measure suggest the need for additional confirmatory research. Further, we found that child externalizing behaviors were the primary correlates of maternal well-being. These findings contribute to the growing body of literature regarding the unique challenges faced by these mother-child dyads and supports the importance of increasing the availability of services available to these mothers, not only for meeting the needs of their children's development and behavior, but in supporting their own well-being as well.

Heart rate variability in patients with atrial fibrillation and hypertension

BACKGROUND

Atrial fibrillation (AF) and hypertension are independently associated with impaired autonomic function determined using heart rate variability (HRV). As these conditions frequently co-exist, we sought to determine whether AF would worsen HRV in hypertensive patients.

DESIGN

We studied HRV in AF (and hypertension) (n = 61) and hypertension control group (n = 33). The AF (and hypertension) group was subdivided into permanent AF (n = 30) and paroxysmal AF (n = 31) and re-studied. Time-domain, frequency-domain and nonlinear measures of HRV were determined. Permanent AF group (n = 30) was followed up after 8 weeks following optimisation of their heart rate and blood pressure (BP).

RESULTS

Time-domain and nonlinear indices of HRV were higher in AF (and hypertension) group compared to hypertensive controls (P ≤ .01). Time-domain and nonlinear indices of HRV were higher in permanent AF group compared to paroxysmal AF (P ≤ .001). Permanent AF was an independent predictor of HRV on multivariable analysis (P = .006). Optimisation of heart rate and BP had no significant impact on HRV in permanent AF.

CONCLUSIONS

AF, independent of hypertension, is characterised with marked HRV and is possibly related to vagal tone. HRV is higher in permanent AF compared to paroxysmal AF suggesting evident autonomic influence in the pathophysiology of permanent AF. Modulation of autonomic influence on cardiovascular system should be explored in future studies.

Alterations in Heart Rate Variability Associated With Irritable Bowel Syndrome or Inflammatory Bowel Disease: A Systematic Review and Meta-Analysis

INTRODUCTION:

Irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD) are gastrointestinal pathologies affecting large numbers of the global population and incurring significant healthcare costs. Disruptions in the gut-brain axis occurring in these conditions can lead to increased inflammation, affecting gastrointestinal and autonomic nervous system function. Heart rate variability (HRV) is commonly used to assess the state of the sympathetic and parasympathetic function of the autonomic nervous system, but it remains unclear how HRV measures are associated with gastrointestinal pathologies. Here, we conduct a systematic review of the literature comparing HRV of subjects diagnosed with IBS or IBD to HRV in healthy controls (HC).

METHODS:

We searched PubMed, Cochrane Library, and CINAHL (EBSCO) for eligible studies up to 2018. We included any study comparing a recognized measure of HRV between a group of patients with either IBS or IBD to a group of matched HC before any intervention. Studies were screened, and data were extracted from included articles using predefined criteria. Random effects meta-analysis was performed for each outcome, with effect size reported as the standardized mean difference.

RESULTS:

There were significant differences between IBD and HC in time domain HRV and significant decreases in high-frequency power measures were also noted, in both IBS and IBD compared with HC.

DISCUSSION:

Parasympathetic nervous system activity, represented through high-frequency power, seems to be lower in people with IBS and IBD, but conclusions are limited by the small number of studies that provide usable data, methodological heterogeneity, and high risks of bias in primary study methods and measures.

fNIRS-based functional connectivity estimation using semi-metric analysis to study decision making by nursing students and registered nurses

This study aims to investigate the generalizability of the semi-metric analysis of the functional connectivity (FC) for functional near-infrared spectroscopy (fNIRS) by applying it to detect the dichotomy in differential FC under affective and neutral emotional states in nursing students and registered nurses during decision making. The proposed method employs wavelet transform coherence to construct FC networks and explores semi-metric analysis to extract network redundancy features, which has not been considered in conventional fNIRS-based FC analyses. The trials of the proposed method were performed on 19 nursing students and 19 registered nurses via a decision-making task under different emotional states induced by affective and neutral emotional stimuli. The cognitive activities were recorded using fNIRS, and the emotional stimuli were adopted from the International Affective Digitized Sound System (IADS). The induction of emotional effects was validated by heart rate variability (HRV) analysis. The experimental results by the proposed method showed significant difference (FDR-adjusted p = 0.004) in the nursing students’ cognitive FC network under the two different emotional conditions, and the semi-metric percentage (SMP) of the right prefrontal cortex (PFC) was found to be significantly higher than the left PFC (FDR-adjusted p = 0.036). The benchmark method (a typical weighted graph theory analysis) gave no significant results. In essence, the results support that the semi-metric analysis can be generalized and extended to fNIRS-based functional connectivity estimation.

Autonomic response to the Adult Attachment Projective in anorexia nervosa

PURPOSE

Cardiovascular complications associated with anorexia nervosa (AN) are well recognized. Whether a wide array of studies has investigated autonomic nervous system (ANS) functioning at rest in people with AN, few is yet known on their reactivity ability during stress conditions. The aim of the current study is testing ANS reactivity to a stressful task activating attachment system among adolescents with AN.

METHODS

Heart rate (HR) and its variability, as derived by high-frequency-heart rate variability (HF-HRV), were continuously assessed while 13 AN patients and 12 healthy controls (HCs) responded to a set of attachment-related drawings (Adult Attachment Projective, AAP).

RESULTS

Findings showed that patients with AN displayed a stronger parasympathetic activity, as indicated by generally a lower heart rate (HR) during the entire task and a higher HF-HRV for drawings eliciting dyadic interactions compared to HCs.

CONCLUSION

The study findings suggest a novel understanding of cardiovascular functioning in AN.

LEVEL OF EVIDENCE

Level V, descriptive study.

Heart rate variability in healthy young adults exposed to global system for mobile communication (GSM) 900-MHz radiofrequency signal from mobile phones

Given the large number of mobile phone users and the increasing exposure to radiofrequency electromagnetic field (RF-EMF) worldwide, we aimed to study the effect of RF-EMF related to mobile phones on heart rate variability (HRV). Twenty-six healthy young adults participated in two experimental sessions with a double-blind, randomized and counter-balanced crossover design. During each session, participants were exposed for 26 min to a sham or real 900 MHz RF-EMF, generated by a commercial dual-band Global System for Mobile technology (GSM) mobile phone. We recorded an electrocardiogram at rest during the exposure. We evaluated HRV by time- and frequency-domain analysis. Evaluation of time-domain HRV parameters revealed a statistically significant increase of the standard deviation of interbeat intervals (SDNN) during the real exposure. Other time-domain parameters were not affected. Analysis in the frequency-domain demonstrated that total spectral power and low-frequency band (LF) absolute power were significantly increased during exposure (p = .046 and p = .043, respectively). However, other parameters were not affected. In conclusion, it seems that most HRV parameters were not affected by GSM signal exposure in our study. The weak effect observed on HRV frequency-domain is likely to represent a random occurrence rather than a real effect.

Heart rate variability with photoplethysmography in 8 million individuals: a cross-sectional study

BACKGROUND

Heart rate variability, or the variation in the time interval between consecutive heart beats, is a non-invasive dynamic metric of the autonomic nervous system and an independent risk factor for cardiovascular death. Consumer wrist-worn tracking devices using photoplethysmography, such as Fitbit, now provide the unique potential of continuously measuring surrogates of sympathetic and parasympathetic nervous system activity through the analysis of interbeat intervals. We aimed to leverage wrist-worn trackers to derive and describe diverse measures of cardiac autonomic function among Fitbit device users.

METHODS

In this cross-sectional study, we collected interbeat interval data that are sent to a central database from Fitbit devices during a randomly selected 24 h period. Age, sex, body-mass index, and steps per day in the 90 days preceding the measurement were extracted. Interbeat interval data were cleaned and heart rate variability features were computed. We analysed heart rate variability metrics across the time (measured via the root mean square of successive RR interval differences [RMSSD] and SD of the RR interval [SDRR]), frequency (measured by high-frequency and low-frequency power), and graphical (measured by Poincare plots) domains. We considered 5 min windows for the time and frequency domain metrics and 60 min measurements for graphical domain metrics. Data from participants were analysed to establish the correlation between heart rate variability metrics and age, sex, time of day, and physical activity. We also determined benchmarks for heart rate variability (HRV) metrics among the users.

FINDINGS

We included data from 8 203 261 Fitbit users, collected on Sept 1, 2018. HRV metrics decrease with age, and parasympathetic function declines faster than sympathetic function. We observe a strong diurnal variation in the heart rate variability. SDRR, low-frequency power, and Poincare S₂ show a significant variation with sex, whereas such a difference is not seen with RMSSD, high-frequency power, and Poincare S₁. For males, when measured from 0600 h to 0700 h, the mean low-frequency power decreased by a factor of 66·5% and high-frequency power decreased by a factor of 82·0% from the age of 20 years to 60 years. For females, the equivalent factors were 69·3% and 80·9%, respectively. Comparing low-frequency power between males and females at the ages of 40-41 years, measured from 0600 h to 0700 h, we found excess power in males, with a Cohen's d effect size of 0·33. For high-frequency power, the equivalent effect size was -0·04. Increased daily physical activity, across age and sex, was highly correlated with improvement in diverse measures of heart rate variability in a dose-dependent manner. We provide benchmark tables for RMSSD, SDRR, high and low frequency powers, and Poincare S₁ and S₂, separately for different ages and sex and computed at two times of the day.

INTERPRETATION

Diverse metrics of cardiac autonomic health can be derived from wrist-worn trackers. Empirical distributions of heart rate variability can potentially be used as a framework for individual-level interpretation. Increased physical activity might yield improvement in heart rate variability and requires prospective trials for confirmation.

FUNDING

Fitbit.

A Critical Review of Ultra-Short-Term Heart Rate Variability Norms Research

Heart rate variability (HRV) is the fluctuation in time between successive heartbeats and is defined by interbeat intervals. Researchers have shown that short-term (∼5-min) and long-term (≥24-h) HRV measurements are associated with adaptability, health, mobilization, and use of limited regulatory resources, and performance. Long-term HRV recordings predict health outcomes heart attack, stroke, and all-cause mortality. Despite the prognostic value of long-term HRV assessment, it has not been broadly integrated into mainstream medical care or personal health monitoring. Although short-term HRV measurement does not require ambulatory monitoring and the cost of long-term assessment, it is underutilized in medical care. Among the diverse reasons for the slow adoption of short-term HRV measurement is its prohibitive time cost (∼5 min). Researchers have addressed this issue by investigating the criterion validity of ultra-short-term (UST) HRV measurements of less than 5-min duration compared with short-term recordings. The criterion validity of a method indicates that a novel measurement procedure produces comparable results to a currently validated measurement tool. We evaluated 28 studies that reported UST HRV features with a minimum of 20 participants; of these 17 did not investigate criterion validity and 8 primarily used correlational and/or group difference criteria. The correlational and group difference criteria were insufficient because they did not control for measurement bias. Only three studies used a limits of agreement (LOA) criterion that specified a priori an acceptable difference between novel and validated values in absolute units. Whereas the selection of rigorous criterion validity methods is essential, researchers also need to address such issues as acceptable measurement bias and control of artifacts. UST measurements are proxies of proxies. They seek to replace short-term values which, in turn, attempt to estimate long-term metrics. Further adoption of UST HRV measurements requires compelling evidence that these metrics can forecast real-world health or performance outcomes. Furthermore, a single false heartbeat can dramatically alter HRV metrics. UST measurement solutions must automatically edit artifactual interbeat interval values otherwise HRV measurements will be invalid. These are the formidable challenges that must be addressed before HRV monitoring can be accepted for widespread use in medicine and personal health care.

Effect on autonomic nervous activity of applying hot towels for 10 s to the back during bed baths

BACKGROUND

Bed baths are a daily nursing activity to maintain patients' hygiene. Those may provide not only comfort but also relaxation. Notably, applying a hot towel to the skin for 10 s (AHT10s) during bed baths helped to reduce the risk of skin tears and provided comfort and warmth in previous studies. However, it is still unclear whether autonomic nervous system is affected by bed baths. Thus, this study investigated the effect on the autonomic nervous activity of applying hot towels for 10 s to the back during bed baths.

METHODS

This crossover study had 50 participants (25 men and women each; average age 22.2 ± 1.6 years; average body mass index 21.4 ± 2.2 kg/m2) who took bed baths with and without (control condition: CON) AHT10s on their back. Skin temperature, heart rate variability (HRV), and blood pressure (BP) were measured. Subjective evaluations and the State-Trait Anxiety Inventory in Japanese were also performed.

RESULTS

A significant interaction of time and bed bath type on skin surface temperature was observed (p < .001). Regarding the means of skin surface temperature at each measurement time point, those for AHT10s were significantly higher than those for CON. Although the total state-anxiety score significantly decreased in both the bed bath types after intervention, the mean values of comfort and warmth were higher for bed baths with AHT10s than for CON (p < .05) during bed baths; AHT10s was significantly higher in warmth than CON after 15 min (p = .032). The interaction and main effects of time on HRV and BP and that of bed bath type were not significant.

CONCLUSION

Bed baths that involved AHT10s caused participants to maintain a higher skin temperature and warmer feeling than under the wiping-only condition; they also provided comfort during the interventions. However, the bed baths with AHT10s did not allow participants to reach a relaxed state; moreover, there was no change in autonomic nerve activity. This may be due to participants' increased anxiety from skin exposure and the intervention being limited to one part of the body.