Reference values for short-term resting-state heart rate variability in healthy adults: Results from the Brazilian Longitudinal Study of Adult Health-ELSA-Brasil study

Reference values for heart rate variability in older adults: A systematic review

Heart rate variability (HRV) is an early marker of risk for various health conditions, and its analysis serves as a valuable tool for assessing older adults. This study aimed to describe the reference values of HRV parameters in older adults through a systematic review of the literature. The review included searches in MEDLINE (via PubMed®), EMBASE, Latin American and Caribbean Health Literature, Scopus, and Web of Science (WOS). Studies presenting reference values for at least one HRV linear analysis measure in older adults were considered eligible. Out of 1618 studies identified, only 11 met the inclusion criteria. Sample sizes of older adults ranged from 21 to 6250 subjects. The HRV measures assessed (mean RR intervals, SDNN, RMSSD, PNN50, LF, HF, and LF/HF ratio) varied significantly between studies, with no standardized methods for HRV analysis. We concluded that reference values for HRV measures in older adults vary widely between studies. The scientific literature on HRV reference values in older adults is still limited, and future studies should standardize assessment methods for HRV measures in this population.

Heart rate variability biofeedback to reduce anxiety in autism spectrum disorder - a mini review

There is a reported high prevalence of anxiety in people with autism spectrum disorder. This mini review appraises existing research investigating heart rate variability biofeedback to help manage symptoms of anxiety in people with autism spectrum disorder. A thorough search of electronic databases was conducted to find relevant literature. Consultation with experts and a librarian helped develop search terms following the PICO framework. Five databases were searched, and screening was undertaken using Covidence software, with the process outlined in a PRISMA flowchart. The latest review showed positive short-term effects but there is a need for long-term follow-up. Future investigations should consider device type, training settings, and control interventions. Accurate heart rate variability assessment independent of biofeedback devices is crucial. Additional measures like cortisol assessment and user feedback are recommended for comprehensive evaluation. The findings highlight progress in the evidence base and offer insight to future directions.

Impact of Obesity on Cardiac Autonomic System Functioning in Military Police Officers

INTRODUCTION

Cardiac autonomic system functioning may be altered by obesity leading to cardiovascular diseases and associated complications. Military police officers are exposed to traditional and occupational risk factors for the development of CVD, however data on the cardiovascular health in this population is still scarce.

AIM

In this cross-sectional study, we investigated the impact of obesity on cardiac autonomic modulation and the hemodynamic profile in male active-duty military police officers.

METHODS

The body composition of the volunteers was assessed by octapolar electrical bioimpedance. Participants were classified as non-obese or obese in accordance with their body fat, with further subgroups as physically active obese or insufficiently active obese using International Physical Activity Questionnaire (IPAQ). Cardiac autonomic modulation was assessed by heart rate variability and the automatic oscillometric method allowed us to assess hemodynamic features.

RESULTS

102 military police officers from the state of São Paulo participated in the study. Cardiac autonomic modulation revealed significant impairment in time and frequency domains and non-linear methods in the obese group compared to the non-obese (p < 0.05). A higher physical activity level did not alter these results in the obese group. However, no significant differences in the hemodynamic profile were observed between groups (p > 0.05).

CONCLUSION

These findings suggest a negative association between obesity and cardiac autonomic modulation in military police officers, unaffected by increased physical activity.

Heart rate variability in patients with insomnia disorder: a systematic review and meta-analysis

BACKGROUND

Though logical inference based on small studies suggests that patients with insomnia have a blunted heart rate variability (HRV), this condition not been clearly shown. This meta-analysis aimed to determine whether or not HRV was impaired in patients with insomnia.

MATERIALS AND METHODS

We conducted a comprehensive literature search for studies that examined the association of HRV with insomnia disorder. HRV measures were extracted using the SDNN (time-domain measure, i.e., standard deviation of all NN intervals,) or the HF-norm (frequency-domain measure, i.e., high-frequency power normalized using total power). The effect size estimates of R_equivalent obtained from p values and sample size were synthesized.

RESULTS

We identified 17 studies with 921 participants. The pooled R_equivalent was 0.19 with 95% CI of 0.12 and 0.25 (p < 0.001), and there was no significant heterogeneity (I2 = 0.0%, p = 0.809). A p value of 0.075 corresponding to the R_equivalent of 0.19 was obtained, suggesting that blunted HRV was not significant in patients with insomnia disorder.

CONCLUSION

The current evidence did not confirm that HRV was reliably impaired in patients with insomnia disorder. Prospective studies using standard HRV measures are needed to clarify the HRV dynamics in different insomnia subtypes.

Do older people with poor sleep quality have worse cardiac autonomic control?

Objective

To identify the differences in cardiac autonomic control between older people with good and poor sleep quality.

Material and Methods

This is a cross-sectional study with 40 older people aged ≥ 60 years, registered at a community health center in Petrolina, Pernambuco, Brazil. The sleep quality was assessed with the Pittsburgh Sleep Quality Index (PSQI). To assess heart rate variability (HRV), the RR intervals (RRI) were recorded for 10 min with a validated smartphone app and a wireless transmitter Polar H7 positioned on the patient's chest. The HRV parameters were calculated with Kubios HRV, and the data were analyzed in SPSS. Subjects with good and poor sleep quality (PSQI >5) were compared with the Mann-Whitney U test.

Results

A total of 31 older people were included in the final analysis, with 18 (58.1%) of them having poor sleep quality. Older people with good sleep quality have similar cardiac autonomic control to those with poor sleep quality. The medians of time (mean RRI, pNN50, SDNN, and RMSSD) and frequency-domain HRV parameters (LFms², LFnu, HFms², HFnu, and LF/HF ratio) were statistically similar (p > .05) in older people with good and poor sleep quality. According to the effect size, the HRV indicators were slightly better among those with good sleep quality.

Conclusion

There were no statistical differences in cardiac autonomic control between older people with good and poor sleep quality.

Association of coronary artery calcium with heart rate variability in the Brazilian Longitudinal Study of Adult Health - ELSA-Brasil

Current data shows that the autonomic and vascular systems can influence each other. However, only a few studies have addressed this association in the general population. We aimed to investigate whether heart rate variability (HRV) was associated with coronary artery calcium (CAC) in a cross-sectional analysis of the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil). We examined baseline data from 3138 participants (aged 35 to 74 years) without previous cardiovascular disease who underwent CAC score assessment and had validated HRV recordings. Prevalent CAC was defined as a CAC score>0, and HRV analyses were performed over 5-min segments. We detected CAC score>0 in 765 (24.4%) participants. Subgroup analyses in older participants (≥49 years) adjusted for sociodemographic and clinical variables revealed that CAC score>0 was associated with lower values of standard deviation of NN intervals (SDNN) (odds ratio [OR]=1.32; 95%CI: 1.05,1.65), root mean square of successive differences between adjacent NN intervals (RMSSD) (OR=1.28; 95%CI: 1.02,1.61), and low frequency (LF) (OR=1.53, 95%CI: 1.21,1.92). Interaction analysis between HRV indices and sex in age-stratified groups revealed significant effect modification: women showed increased OR for prevalent CAC in the younger group, while for men, the associations were in the older group. In conclusion, participants aged ≥49 years with low SDNN, RMSSD, and LF values were more likely to present prevalent CAC, suggesting a complex interaction between these markers in the pathogenesis of atherosclerosis. Furthermore, our results suggested that the relationship between CAC and HRV might be sex- and age-related.

Designing an App to Promote Physical Exercise in Sedentary People Using a Day-to-Day Algorithm to Ensure a Healthy Self-Programmed Exercise Training

Heart rate variability (HRV) has allowed the implementation of a methodology for daily decision making called day-to-day training, which allows data to be recorded by anyone with a smartphone. The purpose of the present work was to evaluate the validity and reliability of HRV measurements with a new mobile app (Selftraining UMH) in two resting conditions. Twenty healthy people (10 male and 10 female) were measured at rest in supine and seated positions with an electrocardiogram and an application for smartphones at the same time (Selftraining UMH) using recordings obtained through an already validated chest-worn heart rate monitor (Polar H10). The Selftraining UMH app showed no significant differences compared to an electrocardiogram, neither in supine nor in sitting position (p > 0.05) and they presented almost perfect correlation levels (r ≥ 0.99). Furthermore, no significant differences were found between ultra-short (1-min) and short (5-min) length measurements. The intraclass correlation coefficient showed excellent reliability (>0.90) and the standard error of measurement remained below 5%. The Selftraining UMH smartphone app connected via Bluetooth to the Polar H10 chest strap can be used to register daily HRV recordings in healthy sedentary people.

Normative values of resting heart rate variability in young male contact sport athletes: Reference values for the assessment and treatment of concussion

Objective

The objective of this study was to identify the main determinants of heart rate variability (HRV) in male athletes aged 14 to 21 years who practice competitive contact sports and to integrate these determinants with the aim of defining normative values of short-term HRV in the time and frequency domains.

Methods

Participants (n = 369) were aged 14 to 21 years and included 221 football players and 148 ice hockey players. HRV was measured for 5 min at rest, and standard HRV parameters in the time and frequency domains were calculated. Heart rate (HR), age, body mass index (BMI), number of sports weekly practices (WSP) and concussion history (mTBI) were considered determinants potentially able to influence HRV.

Results

Multiple regression analysis revealed that HR was the primary determinant of standard HRV parameters. The models accounted for 13% to 55% of the total variance of HRV and the contribution of HR to this model was the strongest (β ranged from -0.34 to -0.75). HR was the only determinant that significantly contributes to all HRV parameters. To counteract this dependence, we calculated HRV corrected by the mean RR interval (RRm). Such corrections do not remove any physiological differences in HRV; they simply remove the mathematical bias. HRV parameters were therefore normalized, and their normative limits were developed relative to the mean heart rate. After correction, the correlation coefficients between HR and all corrected HRV parameters were not statistically significant and ranged from -0.001 to 0.045 (p > 0.40 for all). The automatically corrected HRV calculator, which recalculates standard HRV parameters and converts them into corrected parameters in addition to determining whether a given value is within normal limits, facilitates clinical interpretation.

Conclusion

This study provides for the first time corrected normative values of short-term and resting state HRV parameters in competitive contact sport athletes aged 14 to 21 years. These values were developed independently of the major determinants of HRV. The baseline values for HRV parameters given here could be used in clinical practice when assessing and monitoring cerebral concussions. They may assist in decision making for a safe return to play.

Association between maximal aerobic capacity and heart rate variability

Relevance. Сardiovascular status could be assessed by maximal aerobic capacity (VO2max) through direct analysis of the gases involved in pulmonary ventilation and monitoring fluctuations in intervals between beats over time as heart rate variability. The aim of the study was to investigate the relationship between VO2max and heart rate variability in young adults. Materials and Methods. A total of 100 young adults between the ages of 18 and 25 were included in observational study, who did not engage in any strenuous physical activity, 50 of whom were male and 50 of whom were female.There were measured Heart rate variability in the frequency domain; LF, HF, LF/HF, and time domain; SDNN, RMSSD, pNN 50, and VO2max were assessed using a treadmill test according to Graded Exercise Protocol. Results and Discussion. There was weak positive correlation of VO2max with LF ( r = 0.177) and weak negative correlation with HF ( r = -0.141). Male participants had a weak negative relationship between VO2 max and LF ( r = -0.075), whereas female respondents had a weak positive relationship(r = 0.286). There was weak negative correlation of VO2max with LF/HF ratio for male subjects but weak positive correlation ( r = -0.101) for female subjects. For male and female participants, there was a weak negative association of VO2max with SDNN ( r = -0.170) and ( r = -0.301), respectively. Male and female participants had a weak negative association of VO2max with RMSSD, with ( r = -0.154) and ( r = -0.284) respectively. Male and female participants had a slight negative association of VO2max with pNN 50, with ( r = -0.062) and ( r = -0.441) respectively. Conclusion. Significant variations were found in the time domain and frequency domain indices including HF and LF/HF ratio which represents the balance between sympathetic and parasympathetic responses.

Heart Rate Variability Biofeedback to Treat Anxiety in Young People With Autism Spectrum Disorder: Findings From a Home-Based Pilot Study

Background

People with autism spectrum disorder (ASD) frequently experience high levels of anxiety. Despite this, many clinical settings do not provide specialist ASD mental health services, and demand for professional support frequently outstrips supply. Across many sectors of health, investigators have explored digital health solutions to mitigate demand and extend the reach of professional practice beyond traditional clinical settings.

Objective

This critical appraisal and pilot feasibility study examines heart rate variability (HRV) biofeedback as an approach to help young people with ASD to manage anxiety symptoms outside of formal settings. The aim is to explore the use of portable biofeedback devices to manage anxiety, while also highlighting the risks and benefits of this approach with this population.

Methods

We assessed the feasibility of using home-based HRV biofeedback for self-management of anxiety in young people with ASD. We adopted coproduction, involving people with ASD, to facilitate development of the study design. Next, a separate pilot with 20 participants with ASD (n=16, 80% male participants and n=4, 20% female participants, aged 13-24 years; IQ>70) assessed adoption and acceptability of HRV biofeedback devices for home use over a 12-week period. Data were collected from both carers and participants through questionnaires and interviews; participants also provided single-lead electrocardiogram recordings as well as daily reports through smartphone on adoption and use of their device.

Results

Pre-post participant questionnaires indicated a significant reduction in anxiety in children (t₆=2.55; P=.04; Cohen d=0.99) as well as adults (t₇=3.95; P=.006; Cohen d=0.54). Participant age was significantly negatively correlated with all HRV variables at baseline, namely high-frequency heart rate variability (HF-HRV: P=.02), the root mean square of successive differences in normal heartbeat contractions (RMSSD: P=.02) and the variability of normal-to-normal interbeat intervals (SDNN: P=.04). At follow-up, only SDNN was significantly negatively correlated with age (P=.05). Levels of ASD symptoms were positively correlated with heart rate both before (P=.04) and after the intervention (P=.01). The majority (311/474, 65.6%) of reports from participants indicated that the devices helped when used. Difficulties with the use of some devices and problems with home testing of HRV were noted. These initial findings are discussed within the context of the strengths and challenges of remotely delivering a biofeedback intervention for people with ASD.

Conclusions

HRV biofeedback devices have shown promise in this pilot study. There is now a need for larger evaluation of biofeedback to determine which delivery methods achieve the greatest effect for people with ASD.

Trial Registration

ClinicalTrials.gov NCT04955093; https://clinicaltrials.gov/ct2/show/NCT04955093

Objective Measurement of Learners' Cognitive Load During Simulation-Based Trauma Team Training: A Pilot Study

INTRODUCTION

Literature has shown cognitive overload which can negatively impact learning and clinical performance in surgery. We investigated learners' cognitive load during simulation-based trauma team training using an objective digital biomarker.

METHODS

A cross-sectional study was carried out in a simulation center where a 3-h simulation-based interprofessional trauma team training program was conducted. A session included three scenarios each followed by a debriefing session. One scenario involved multiple patients. Learners wore a heart rate sensor that detects interbeat intervals in real-time. Low-frequency/high-frequency (LF/HF) ratio was used as a validated proxy for cognitive load. Learners' LF/HF ratio was tracked through different phases of simulation.

RESULTS

Ten subjects participated in 12 simulations. LF/HF ratios during scenario versus debriefing were compared for each simulation. These were 3.75 versus 2.40, P < 0.001 for scenario 1; 4.18 versus 2.77, P < 0.001 for scenario 2; and 4.79 versus 2.68, P < 0.001 for scenario 3. Compared to single-patient scenarios, multiple-patient scenarios posed a higher cognitive load, with LF/HF ratios of 3.88 and 4.79, P < 0.001, respectively.

CONCLUSIONS

LF/HF ratio, a proxy for cognitive load, was increased during all three scenarios compared to debriefings and reached the highest levels in a multiple-patient scenario. Using heart rate variability as an objective marker of cognitive load is feasible and this metric is able to detect cognitive load fluctuations during different simulation phases and varying scenario difficulties.

Autonomic and cardiorespiratory responses to the active tilt test in individuals with Parkinson disease: cross-sectional study

BACKGROUND

The Parkinson disease (PD) is frequently associated with autonomic dysfunctions. However, data regarding the influence of PD on the autonomic responses to postural changes is limited.

OBJECTIVE

To analyze and compare the autonomic responses, evaluated through linear and non-linear methods of heart rate variability, and cardiorespiratory parameters in two groups: Parkinson disease (PDG) and control (CG), at rest and during the active tilt test.

METHODS

A total of 48 participants were analyzed (PDG: n = 25;73.40 ± 7.01 years / CG: n = 23;70.17 ± 8.20 years). The autonomic modulation and cardiorespiratory parameters were evaluated at rest and during the active tilt test. To assess the autonomic modulation the linear indices, at the time (rMSSD, SDNN) and frequency (LF, HF, LF/HF) domains, and the non-linear indices, obtained through the Poincaré plot (SD1, SD2, SD1/SD2), were calculated. The cardiorespiratory parameters evaluated were heart rate (HR), systolic (SBP), and diastolic blood pressure (DBP), peripheral oxygen saturation (SpO₂), and respiratory rate.

RESULTS

At rest, the PDG presented significantly lower values of rMSSD, SDNN, LF, HF, SD1, SD2, and DBP, and higher values of SpO₂. During test, in the PD group, modifications were observed in HR, and SBP, besides a reduced parasympathetic response, and an increased global modulation. The qualitative analysis of the Poincaré plot showed that the PDG has a lower dispersion of the RR intervals during rest and the active tilt test.

CONCLUSION

Individuals with PD present reduced global variability and parasympathetic modulation at rest, and reduced parasympathetic response and damage in HR regulation when performing the active tilt test, compared with controls.

Different exercise training modalities similarly improve heart rate variability in sedentary middle-aged adults: the FIT-AGEING randomized controlled trial

PURPOSE

This study aimed to investigate the influence of different exercise training modalities on heart rate variability (HRV) in sedentary middle-aged adults; and to study whether changes in health-related outcomes (i.e., body composition and cardiometabolic risk) are associated with those hypothetical HRV changes in sedentary middle-aged adults.

METHODS

A total of 66 middle-aged adults (53.6 ± 4.4 years old; 50% women) were enrolled in the FIT-AGEING study. We conducted a 12-week randomized controlled trial. The participants were randomly assigned to 4 groups: (a) a control group (no exercise); (b) a physical activity recommendation from the World Health Organization group (PAR); (c) a high-intensity interval training group (HIIT); and (d) a high-intensity interval training group adding whole-body electromyostimulation (HIIT + EMS).

RESULTS

All exercise training modalities induced changes in HRV parameters (all P ≤ 0.001) without statistical differences between them (all P > 0.05). We found associations between changes in body composition and cardiometabolic risk and exercise-related changes in HRV.

CONCLUSION

Our results suggest that different exercise interventions (i.e., PAR, HIIT and HIIT + EMS) induced an enhancement of HRV in sedentary middle-aged adults. Our findings support the notion that exercise-related changes in HRV are associated with changes in body composition and cardiometabolic risk after the intervention program CLINICAL TRIAL REGISTRY: NCT03334357 (ClinicalTrials.gov). November 7, 2017 retrospectively registered.

Randomized Pilot Trial Using External Yarrow Liver Compress Applications With Metastatic Cancer Patients Suffering From Fatigue: Evaluation of Sympathetic Modulation by Heart Rate Variability Analysis

Background:

Liver compresses are commonly applied in complementary medicine during cancer treatment and are believed to have an energizing effect. We conducted a pilot study to investigate the influence of external application of yarrow liver compresses on the autonomous nervous system by analyzing the heart rate variability (HRV) in metastatic cancer patients undergoing radiation therapy and suffering from cancer-related fatigue (CRF).

Methods:

A randomized pilot trial was undertaken with patients suffering from CRF receiving palliative radiation therapy for bone or brain metastasis over 2 weeks. CRF patients were randomized into an intervention group receiving yarrow liver compresses and a control group receiving no external application. HRV was analyzed at the beginning (T1) and end (T2) period of the study during daytime (d) and nighttime (n) in both groups and quantified using time-, frequency-, and nonlinear dynamics domains.

Results:

A total of 39 patients were randomized between September 2017 and August 2019 and a total of 20 patients (10 per group) were available for analysis. For both groups, significant differences in HRV analyses were found in the comparison over the timeline between the first and second measurement (T1d→T2d) during daytime. Specifically, the intervention group showed decreased HRV and complexity of heart rate regulation, indicating increased sympathetic activity at time T2d, whereas the control group showed increased HRV and complexity of heart rate regulation, indicating increased vagal activity at time T2d. Furthermore, the observed HRV analyses showed almost no significant differences between the 2 groups in a direct comparison at the beginning and the end of the study (exception: T2d).

Conclusions:

Yarrow liver compresses led to increased sympathetic activity during daytime in the intervention group, whereas in the control group, which did not receive any external application, increased parasympathetic activity was observed.

How predictable is heart rate variability in Brazilian patients with drug-resistant mesial temporal lobe epilepsy?

This study aimed to compare heart rate variability (HRV) in patients with drug-resistant mesial temporal lobe epilepsy (MTLE) with healthy controls and to analyze their clinical and sociodemographic variables predictive for HRV. Thirty-nine consecutive patients with drug-resistant MTLE were included in the study. The control group included twenty-seven healthy participants matched by age and gender. Seven HRV indices (HR, RR, rMSSD, SDNN, LF, HF, and LF/HF) were compared between patients and controls. The clinical and sociodemographic variables independently associated with the HRV indices were identified by multiple linear regression. In comparison with controls, the patients with MTLE showed a significant reduction in RR, rMSSD, SDNN, LF, HF, and LF/HF indices (t value 1.97-5.97, p < 0.05). Multiple regression models showed that disease duration predicted 11-22% of the analyzed HRV indices. Time domain indices showed higher association with disease duration than coefficients in frequency domain. Patients with drug-resistant MTLE present cardiac autonomic tone dysfunction, showing a significant reduction in their HRV indices (RR, SDNN, rMSSD, LF, HF, and LF/HF). Disease duration has a negative association with all HRV indices. This study contributes to understanding the relationship between MTLE and the cardiac autonomic tone, with possible implications for sudden unexpected death in epilepsy.

Intensive chemotherapy perturbs heart rate variability in children with cancer

OBJECTIVES

In children, cancer chemotherapy may impair the functioning of the cardiac autonomic nervous system. Moreover, it is not known whether there are any differences between intensive and maintenance phases of chemotherapy. Therefore, the aim of the current study was to assess autonomic nervous system activity using heart rate variability, in children receiving intensive or maintenance cancer chemotherapy.

METHODS

For that purpose, children who were healthy (healthy control, n = 30), receiving intensive chemotherapy (chemotherapy, n = 30), and receiving maintenance chemotherapy (maintenance, n = 25) were included in the study. Autonomic nervous system activity was measured by means of heart rate variability. Electrocardiogram recordings were used to calculate time- and frequency-domain heart rate variability parameters.

RESULTS

Time-domain parameters such as standard deviation of NN intervals and frequency-domain parameters such as total power were lower during the intensive chemotherapy but not during maintenance phase (standard deviation of NN intervals: 50±5, 33±3, and 48±3 ms, and total power: 2613±504, 1379±296 and 2295±264 ms², respectively for healthy control, chemotherapy and maintenance groups, P<0.001 for both standard deviation of NN intervals and total power).

DISCUSSION

The present results indicate that intensive chemotherapy perturbs the function of heart rate variability in children, with recovery during the maintenance phase. This suggests that intensive chemotherapy is likely to affect the autonomic nervous system but this effect does not appear to be permanent.

Heart Rate Variability and Cardiovascular Fitness: What We Know so Far

Fluctuation analysis in intervals between heartbeats provides important indices related to autonomic modulation of heart rate variability (HRV). These indices are considered predictors of morbidity and mortality as they are frequently altered in patients with chronic degenerative diseases, especially in those with cardiovascular and metabolic diseases. Similarly, a reduction in HRV is common with aging. In all cases, cardiovascular fitness is often reduced to below the predicted values. In turn, increases in cardiovascular fitness through regular physical exercise, especially aerobic exercise, represent an important therapeutic tool capable of promoting positive adjustments in cardiac autonomic modulation. These adjustments are characterized by reduced sympathetic modulatory influence and/or increased vagal modulatory influence on the heart, increasing the HRV. Therefore, several methodological tools have been used to assess the degree of impairment of autonomic modulation and the therapeutic effects of physical exercise. In contrast, establishment of strict protocols in experimental design is a main challenge in establishing HRV analysis as a robust parameter for evaluating cardiovascular homeostasis. Thus, this review aimed to contribute to the understanding of autonomic modulation of HRV and its relationship with cardiovascular fitness, highlighting the advances made thus far, the applicability of analysis tools, and the confounding factors observed frequently.

The Use of Cardiac Autonomic Responses to Aerobic Exercise in Elderly Stroke Patients: Functional Rehabilitation as a Public Health Policy

Background and purpose: The development of public policies must be guided by full knowledge of the health–disease process of the population. Aerobic exercises are recommended for rehabilitation in stroke patients, and have been shown to improve heart rate variability (HRV). Our aim was to compare the cardiac autonomic modulation of elderly stroke patients with that of healthy elderly people during and after an acute bout of aerobic exercise. Methods: A total of 60 elderly people participated in the study (30 in the control group, mean age of 67 ± 4 years; 30 in the stroke group, mean age of 69 ± 3 years). HRV was analyzed in rest—10 min of rest in supine position; exercise—the 30 min of peak exercise; and recovery—30 min in supine position post-exercise. Results: Taking rest and exercises together, for SDNN, RMSSD, pNN50, RRTri, and TINN, there was no difference between the stroke and control groups (p = 0.062; p = 0.601; p = 0.166; p = 0.224, and p = 0.059, respectively). The HF (ms²) was higher and the LF/HF ratio was lower for the stroke group than the control group (p < 0.001 and p = 0.007, respectively). The SD2 was lower for the stroke group than for the control group (p = 0.041). Conclusion: Stroke patients present reduced variability at rest, sympathetic predominance during exercise, and do not return to baseline after the 30 min of recovery, with similar responses found in the healthy elderly group.

The Cognitive Relevance of a Formal Pre-incision Time-out in Surgery

Surgical time-outs are designed to promote situation awareness, teamwork, and error prevention. The pre-incision time-out in particular aims to facilitate shared mental models prior to incision. Objective, unbiased measures to confirm its effectiveness are lacking. We hypothesized that providers’ mental workload would reveal team psychophysiological mirroring during a formal, well-executed pre-incision time-out. Heart rate variability was collected during cardiac surgery cases from the surgeon, anesthesiologist, and perfusionist. Data were analyzed for six cases from patient arrival until sternal closure. Annotation of surgical phases was completed according to previously developed standardized process models of aortic valve replacement and coronary artery bypass graft procedures, producing thirteen total surgical phases. Statistical analysis revealed significant main effects. Tukey HSD post hoc tests revealed significant differences across provider roles within various phases, including Anesthesia Induction, Heparinization, Initiation of Bypass, Aortic Clamp and Cardioplegia, Anastomoses or Aortotomy, Separation from Bypass, and Sternal Closure. Despite these observed differences between providers over various surgical phases, the Pre-incision Time-out phase revealed almost negligible differences across roles. This preliminary work supports the utility of the pre-incision safety checklist to focus the attention of surgical team members and promote shared team mental models, measured via psychophysiological mirroring, using an objective mental workload measure. Future studies should investigate the relationship between psychophysiological mirroring among surgical team members and the effectiveness of the pre-incision time-out checklist.

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.

Ultra-short heart rate variability reliability for cardiac autonomic tone assessment in mesial temporal lobe epilepsy

Autonomic dysfunction in epilepsy is well-described. Heart rate variability (HRV) is a useful method to evaluate autonomic cardiac tone. Cardiac dysfunction may be involved in sudden unexpected death in epilepsy (SUDEP). HRV is a promising biomarker to enlighten the heart-brain axis role in SUDEP, but the required duration for a proper HRV recording in clinical routine remains unknown. This study aimed to verify the reliability of ultra-short HRV indices to evaluate cardiac autonomic tone in patients with epilepsy (PWE). Thirty-nine patients with mesial temporal lobe epilepsy (MTLE) had electrocardiogram recordings during the first day of video-EEG. Pearson's correlations were performed to evaluate the association between ultra-short HRV indices (five 1-min and five 30-s epochs) with standard time recording (5-min) and ANOVA compared the differences between mean HRV indices across epochs. Time domain (TD) indices showed higher mean r values when compared to frequency domain (FD) indices in 1-min (TD: r 0.80-0.99, FD: r 0.61-0.95) and 30-s epochs (TD: r 0.69-0.99, only high frequency: mean r values of 0.96). ANOVA evidenced that standard deviation of RR intervals and very low frequency means had at least 3 epochs significantly different for 1-min and 30-s epochs. Root mean square of the successive differences of RR intervals (rMSSD) presented higher Pearson's coefficient values and lower percentage of variation at 1-min or 30-s epochs in comparison to other HRV indices. In conclusion, rMSSD is the most reliable ultra-short HRV index for cardiac autonomic tone assessment in MTLE. The prognostic value of ultra-short HRV for cardiovascular risk evaluation in epilepsy remains to be determined in future studies.

Heart rate variability and oxygen reserve index during cardiorespiratory events in patients undergoing ophthalmic arterial chemotherapy: a prospective observational study

Unexpected cardiorespiratory compromise has been reported during ophthalmic arterial chemotherapy in pediatric patients with retinoblastoma. Although the underlying mechanisms remain unclear, autonomic responses are presumed to contribute to these events. We hypothesized that periprocedural heart rate variability would differ between patients with and without events. Between April 2018 and September 2019, 38 patients (age under 7 years) were included. Heart rate variability was analyzed using electrocardiogram, and oxygen reserve index was also monitored. Cardiorespiratory events were defined as > 30% changes in blood pressure or heart rate, > 20% changes in end-tidal carbon dioxide, > 40% changes in peak inspiratory pressure, or pulse oxygen saturation < 90% during ophthalmic artery catheterization. Heart rate variability and oxygen reserve index were compared between patients with and without cardiorespiratory events. Cardiorespiratory events occurred in 13/38 (34%) patients. During the events, end-tidal carbon dioxide was significantly lower (median difference [95% CI], - 2 [- 4 to - 1] mmHg, p = 0.006) and the maximum peak inspiratory pressure was higher (30 [25-37] vs. 15 [14-16] hPa, p < 0.001), compared to patients without events. Standard deviation of normal-to-normal R-R interval, total power, and very low-frequency power domain increased during selection of the ophthalmic artery in patients with events (all adjusted p < 0.0001), without predominancy of specific autonomic nervous alterations. Oxygen reserve index was significantly lower in patients with events than those without throughout the procedure (mean difference [95% CI], - 0.19 [- 0.32 to - 0.06], p = 0.005). Enhanced compensatory autonomic regulation without specific autonomic predominancy, and reduced oxygen reserve index was observed in patients with cardiorespiratory events than in patients without events.

Reduced heart-rate variability and increased risk of hypertension-a prospective study of the ELSA-Brasil

Although autonomic disturbances are known to precede hypertension onset, the risks underlying different ranges of blood pressure and impaired cardiac autonomic modulation are still unknown. This study aimed to identify the risk of hypertension incidence related to low heart-rate variability profile in normotensive blood pressure subcategories: normal (<120/80 mmHg) and prehypertension (120/80-139/89 mmHg) in a 4-year follow-up. 7665 participants free of hypertension at baseline were examined. They were allocated into one of two groups (<P25 and ≥P25) based on age-specific value distributions of heart-rate variability ranges presented in the literature. The relationship between heart-rate variability parameters (SDNN, RMSSD, VLF, LF, and HF) and hypertension incidence was analyzed using Poisson regression. The reference for the independent variable in these regressions was the dataset with all HRV values ≥P25. After full adjustments for age, sex, ethnicity, educational level, body mass index, smoking status, glucose, insulin, dyslipidemia, alcohol consumption, and physical activity, low values for all heart-rate variability indices were significantly associated with an increased relative risk of developing hypertension in the overall sample. Individuals with normal BP levels presented an increased risk for low SDNN, VLF, and LF values, whereas the risk in prehypertensive participants was only verified for low VLF. In conclusion, cardio autonomic disturbances precede the incidence of clinical hypertension and are potentially involved in its pathophysiological basis and progression. Even individuals with normal blood pressure may be at an increased risk for future hypertension in the presence of reduced cardio autonomic control.

Heart Rate Variability Modulates Interoceptive Accuracy

Our emotional experiences depend on our interoceptive ability to perceive and interpret changes in our autonomous nervous system. An inaccurate perception and interpretation of autonomic changes impairs our ability to understand and regulate our emotional reactions. Impairments in emotion understanding and emotion regulation increase our risk for mental disorders, indicating that interoceptive deficits play an important role in the etiology and pathogenesis of mental disorders. We, thus, need measures to identify those of us whose interoceptive deficits impair their emotion understanding and emotion regulation. Here, we used cardiac measures to investigate how our ability to engage prefrontal and (para-)limbic brain region regions affects our ability to perceive and interpret cardiac changes. We administered a heartbeat detection task to a sample of healthy individuals (n = 113) whose prefrontal-(para-) limbic engagement had been determined on basis of a heart rate variability recording. We found a positive association between heartbeat detection and heart rate variability, implying that individuals with higher heart rate variability were more accurate in heartbeat detection than individuals with lower heart rate variability. These findings suggest that our interoceptive accuracy depends on our prefrontal-(para-)limbic engagement during the perception and interpretation of cardiac changes. Our findings also show that cardiac measures may be useful to investigate the association between interoceptive accuracy and prefrontal-(para-)limbic engagement in a time- and cost-efficient manner.

Diabetes and subclinical hypothyroidism on heart rate variability

BACKGROUND

We aimed to analyse if the effects of coexistent diabetes and subclinical hypothyroidism extend to the cardio autonomic nervous system, using heart rate variability baseline data from the Brazilian Longitudinal Study of Adult Health.

MATERIALS AND METHODS

Heart rate variability analyses were performed by linear time and frequency domains in 5-minute time series collected in the supine position. The associations of diabetes and subclinical hypothyroidism with the lowest quartile group for heart rate and the highest quartile group for each heart rate variability parameter were analysed using additive and multiplicative terms in logistic models. For the first approach, the subsample was categorized into four groups: subjects without diabetes and normal thyroid function (controls); subjects without diabetes and subclinical hypothyroidism; patients with diabetes and normal thyroid function; and patients with diabetes and subclinical hypothyroidism. For the interaction alnalysis, diabetes and subclinical hypothyroidism diagnoses were included in separate, along with a multiplicative interaction term between them.

RESULTS

Point odds ratio estimates for the 4th quartiles of heart rate, and 1st quartiles of all heart rate variability measurements were higher for subjects with combined diabetes and subclinical hypothyroidism than for diabetes only, independently of main sociodemographic and clinical variables (HR: 8.33 vs 2.63; SDNN: 2.59 vs 1.61; RMSSD: 2.37 vs 1.42; LF: 2.83 vs 1.71; HF: 3.06 vs 1.39), but not independently of HbA1c and TSH. Only the interaction term for the association with heart rate, adjusted for sociodemographic and clinical variables, had borderline statistical significance.

CONCLUSION

Diabetes and subclinical hypothyroidism exert a potential joint impact on cardiac autonomic control, showed by additive effects between diabetes and subclinical hypothyroidism, as well as a significant interaction term for the association with heart rate.

Assessment of autonomous nerve system through non-linear heart rate variability outcomes in sedentary healthy adults

Background

Heart rate variability (HRV) is a psycho-physiological phenomenon with broad health implications. Different data analysis methods have been used to assess the autonomic nervous system activity, but the validation of new indexes that accurately describe its balance through non-invasive methods (i.e., HRV analysis) is of clinical interest. This study aimed: (i) to evaluate the association of the Stress Score (SS) and the Sympathetic/Parasympathetic Ratio (S/PS) with time domain and frequency domain analysis of HRV, and (ii) to set reference values of SS and S/PS in sedentary healthy adults.

Methods

A total of 156 sedentary healthy adults (38.4 ± 15.57 years old, 81 women), aged were involved in this study. HRV was measured for 15 min in a supine position at rest. SS and S/PS were calculated from the non-linear HRV analyses based on Poincare Plot.

Results

Stress Score showed a non-linear negative power-law relationship with SDNN (β = -0.969; R ² = 0.963; P < 0.001), RMSSD (β = -0.867; R ² = 0.722; P < 0.001), high frequency (β = -0.834; R ² = 0.752; P =< 0.001), low frequency (β = -0.627; R ² = 0.330; P < 0.001), SD1 (β = -0.867; R ² = 0.722; P < 0.001) and SD2 (β = -1.000; R ² > 0.999; P < 0.001). There was observed a negative cubic relationship between SS with PNN50 (β = -1.972; R ² = 0.644; P < 0.001). A linear regression model was conducted between SS with Ratio Low/High Frequency (β = 0.026; R ² < 0.001; P = 0.750). Non-linear power-law regression models were built between S/PS and SDNN (β = -0.990; R ² = 0.981; P < 0.001), RMSSD (β = -0.973; R ² = 0.939; P < 0.001), high frequency (β = -0.928; R ² = 0.970; P < 0.001), low frequency (β = -2.344; R ² = 0.557; P < 0.001), SD1 (β = -0.973; R ² = 0.939; P < 0.001) and SD2 (β = -0.611; R ² = 0.908; P < 0.001). A non-linear negative regression model was built between S/PS and PNN50 (β = -3.412; R ² = 0.868; P < 0.001). A linear regression model was conducted between S/PS and SD2/SD1 (β = 0.075; R ² = 0.006; P < 0.001).

Conclusion

Our results support the use of SS as a sympathetic activity marker, and S/PS as an indicator of the sympathetic and parasympathetic activity of the autonomic nervous system in sedentary healthy adults.

Assessment of a dive incident using heart rate variability

INTRODUCTION

Scuba diving likely has an impact on the autonomic nervous system (ANS). In the course of conducting trials of underwater ECG recording for measurement of heart rate variability, there was an unexpected stressful event; one participant's regulator iced and began to free-flow.

METHODS

A custom-made, water- and pressure-tight aluminum housing was used to protect a portable Holter monitor. ECGs were recorded in three experienced divers who witnessed an unplanned moderately stressful incident during diving. The ECG signals were analysed for measures of heart rate variability (HRV).

RESULTS

Analysis for different short-term HRV measures provided consistent results if periods of interest were appropriately time-aligned. There was improvement in sympatho-vagal balance. One diver unexpectedly exhibited an increase in both sympathetic and vagal activity shortly after the incident.

CONCLUSIONS

A conventional open-water dive affected the ANS of experienced recreational divers as measured by HRV which provides a global evaluation of the ANS and alterations in its two branches. The heart rate variability data gathered from several participating divers around the time of this event illustrate the potential utility of this variable in quantifying stress during diving. HRV data may be useful in addressing relevant diving related questions such as effects of cold, exercise or different breathing gases on ANS function.

Age and Sex Differences in Heart Rate Variability and Vagal Specific Patterns - Baependi Heart Study

Background

Heart rate variability (HRV) is a noninvasive method for assessing autonomic function. Age, sex, and chronic conditions influence HRV.

Objectives

Our aim was to evaluate HRV measures exploring differences by age, sex, and race in a sample from a rural area.

Methods

Analytical sample (n = 1,287) included participants from the 2010 to 2016 evaluation period of the Baependi Heart Study, a family-based cohort in Brazil. Participants underwent 24-hour Holter-ECG (Holter) monitoring. To derive population reference values, we restricted our analysis to a 'healthy' subset (i.e. absence of medical comorbidities). A confirmatory analysis was conducted with a subgroup sample that also had HRV derived from a resting ECG 10'-protocol obtained during the same time period.

Results

The 'healthy' subset included 543 participants. Mean age was 40 ± 14y, 41% were male, 74% self-referred as white and mean body-mass-index was 24 ± 3kg/m². Time domain HRV measures showed significant differences by age-decade and by sex. Higher values were observed for males across almost all age-groups. Parasympathetic associated variables (rMSSD and pNN50) showed a U-shaped distribution and reversal increase above 60y. Sympathetic-parasympathetic balance variables (SDNN, SDANN) decreased linearly by age. Race differences were no significant. We compared time domain variables with complete data (Holter and resting ECG) between 'healthy' versus 'unhealthy' groups. Higher HRV values were shown for the 'healthy' subset compared with the 'unhealthy' group.

Conclusion

HRV measures vary across age and sex. A U-shaped pattern and a reversal increase in parasympathetic variables may reflect an age-related autonomic dysfunction even in healthy individuals that could be used as a predictor of disease development.

Autonomic Activity and Surgical Flow Disruptions in Healthcare Providers during Cardiac Surgery

Cardiac surgery represents a complex sociotechnical environment relying on a combination of technical and non-technical team-based expertise. Surgical flow disruptions (SFDs) may be influenced by a variety of sources, including social, environmental, and emotional factors affecting healthcare providers (HCPs). Many of these factors can be readily observed, except for emotional factors (i.e. distress), which represents an underappreciated yet critical source of SFDs. The aim of this study was to demonstrate the sensitivity of autonomic activity metrics to detect an SFD during cardiac surgery. We integrated heart rate variability (HRV) analysis with observation-based annotations to allow data triangulation. Following a critical medication administration error by the anesthesiologist in-training, data sources were consulted to identify events precipitating this near-miss event. Using pyphysio, an open-source physiological signal processing package, we analyzed the attending anesthesiologists' HRV, specifically the low frequency (LF) power, high frequency (HF) power, LF/HF ratio, standard deviation of normal-to-normal (SDNN), and root mean square of the successive differences (RMSSD) as indicators of ANS activity. A heightened SNS response in the attending anesthesiologists' physiological arousal was observed as elevations in LF power and LF/HF ratio, as well as depressions in HF power, SDNN, and RMSSD prior to the near-miss event. The attending anesthesiologist subjectively confirmed a state of high distress induced by task-irrelevant environmental factors during this time. Qualitative analysis of audio/video recordings objectively revealed that the autonomic nervous system (ANS) activation detected was temporally associated with an argument over operating room management. This study confirms that it is possible to recognize detrimental psychophysiological influences in cardiac surgery procedures via advanced HRV analysis. To our knowledge, ours is the first such case demonstrating ANS activity coinciding with strong self-reported emotion during live surgery using HRV. Despite extensive experience in the cardiac OR, transient but intense emotional changes may have the potential to disrupt attention processes in even the most experienced HCP. A primary implication of this work is the possibility to detect real-time ANS activity, which could enable personalized interventions to proactively mitigate downstream adverse events. Additional studies on our large database of surgical cases are underway and new studies are actively being planned to confirm this preliminary observation.

Heart Rate Variability Triangular Index as a Predictor of Cardiovascular Mortality in Patients With Atrial Fibrillation

Background

Impaired heart rate variability (HRV) is associated with increased mortality in sinus rhythm. However, HRV has not been systematically assessed in patients with atrial fibrillation (AF). We hypothesized that parameters of HRV may be predictive of cardiovascular death in patients with AF.

Methods and Results

From the multicenter prospective Swiss‐AF (Swiss Atrial Fibrillation) Cohort Study, we enrolled 1922 patients who were in sinus rhythm or AF. Resting ECG recordings of 5‐minute duration were obtained at baseline. Standard parameters of HRV (HRV triangular index, SD of the normal‐to‐normal intervals, square root of the mean squared differences of successive normal‐to‐normal intervals and mean heart rate) were calculated. During follow‐up, an end point committee adjudicated each cause of death. During a mean follow‐up time of 2.6±1.0 years, 143 (7.4%) patients died; 92 deaths were attributable to cardiovascular reasons. In a Cox regression model including multiple covariates (age, sex, body mass index, smoking status, history of diabetes mellitus, history of hypertension, history of stroke/transient ischemic attack, history of myocardial infarction, antiarrhythmic drugs including β blockers, oral anticoagulation), a decreased HRV index ≤ median (14.29), but not other HRV parameters, was associated with an increase in the risk of cardiovascular death (hazard ratio, 1.7; 95% CI, 1.1–2.6; P=0.01) and all‐cause death (hazard ratio, 1.42; 95% CI, 1.02–1.98; P=0.04).

Conclusions

The HRV index measured in a single 5‐minute ECG recording in a cohort of patients with AF is an independent predictor of cardiovascular mortality. HRV analysis in patients with AF might be a valuable tool for further risk stratification to guide patient management.

Registration

URL: https://www.clinicaltrials.gov; Unique identifier: NCT02105844.

Feasibility of Healthcare Providers' Autonomic Activation Recognition in Real-Life Cardiac Surgery Using Noninvasive Sensors

Cardiac surgery is one of the most complex specialties in medicine, akin to a complex sociotechnical system. Patient outcomes are vulnerable to surgical flow disruptions (SFDs), a source of preventable harm. Healthcare providers' (HCPs) sympathetic activation secondary to emotional states represent an underappreciated source of SFDs. This study's objective was to demonstrate the feasibility of detecting elevated sympathetic nervous system (SNS) activity as a proxy for emotional distress associated with a medication error using heart rate variability (HRV) analysis. After obtaining informed consent, audio/video and HRV data were captured intraoperatively during cardiac surgery from multiple HCPs. Following a critical medication administration error by the anesthesiologist in-training, the attending anesthesiologists' recorded HRV data was analyzed using pyphysio, an open-source signal analysis package, to identify events precipitating this near-miss event. We considered elevated low-frequency/high-frequency (LF/HF) HRV ratio (normal value <2) as a primary indicator of SNS activity and emotional distress. A heightened SNS response by the attending anesthesiologist, observed as an LF/HF ratio value of 3.39, was detected prior to the near-miss event. The attending anesthesiologist confirmed a state of significant SNS activity/distress induced by task-irrelevant environmental factors, which led to a temporarily ineffective mental model. Qualitative analysis of audio/video recordings revealed that SNS activation coincided with an argument over operating room management causing SFD. This preliminary study confirms the feasibility of recognizing potentially detrimental psychophysiological states during cardiac surgery in the wild using HRV analysis. To our knowledge, this is the first case demonstrating SNS activation coinciding with self-reported and observable emotional distress during live surgery using HRV. Irrespective of the HCP's expertise, transient but intense emotional changes may disrupt attention processes leading to SFDs and preventable errors. This work supports the possibility to detect real-time SNS activation, which could enable interventions to proactively mitigate errors. Additional studies on our large database of surgical cases are underway to confirm this observation.

Job Stress and Heart Rate Variability: Findings From the ELSA-Brasil Cohort

OBJECTIVE

Evidence suggests that exposure to psychosocial stress at work can inhibit vagal tonus, influencing the capacity to respond to environmental stimuli. We investigated whether job strain and low control and high demand at work, as separate measures, are associated with a reduction in heart rate variability (HRV).

METHODS

This is a cross-sectional study with 9658 active workers at the baseline (2008-2010) of the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil). HRV was estimated using electrocardiographic recordings for 10 minutes, at rest, examining the following indices were used: root mean square of successive difference, standard deviation of normal to normal, percentage of adjacent R-R intervals with a difference lasting more than 50 ms, low frequency (LF), and high frequency. Job strain was defined based on the demand-control model. Independent associations between job strain and HRV indices were verified using generalized linear models and the magnitude of the association was estimated by evaluating the ratios of arithmetic means.

RESULTS

Neither the unfavorable demand-control relation nor job demand dimension separately was associated with HRV. However, the increase of one unit in the control dimension was associated with an increment of 2.2% (95% confidence interval = 1.014-1.029) in the LF mean. After adjustments for sociodemographic characteristics, assessment site, health-related behaviors, and depression, this association remained statistically significant (ratio of arithmetic means = 1.008; 95% confidence interval = 1.0002-1.017).

CONCLUSIONS

Job control was associated with HRV in a large cohort of civil servants. Nevertheless, it is important to emphasize that only the LF index remained associated with low job control. Further studies are needed to develop a greater understanding of the relationship of psychosocial aspects and autonomic balance.

Short-term Heart-rate Variability in Healthy Small and Medium-sized Dogs Over a Five-minute Measuring Period

Introduction

Five-minute heart-rate variability (HRV) measurement is a useful tool for assessing the autonomic nervous system (ANS) balance in humans, but there are no studies on healthy dogs. The aim of the study was, therefore, to provide the reference ranges in small and medium-sized breeds for short-term HRV time and frequency domain (TFD) analyses.

Material and Methods

A total of 79 healthy dogs were included in the study between 2015 and 2019. Grouping by age with the breakpoint at six years and subgrouping by reproductive status and sex was imposed. All the dogs were included after physical and cardiological examinations and blood analyses. The TFD of HRV were analysed from a five-minute-long digital ECG recording after removal of non-sinus complexes.

Results

There were no statistically significant differences in any TFD parameters between age, reproductive status or sex groups. A mild increase in all time domain parameters and the high-frequency (HF) band was observed in older dogs, and the low frequency (LF):HF ratio decreased in these dogs. In males, the time domain parameters and HF band increased slightly.

Conclusion

The normal ranges for HRV derived from short-term ECG recording in the usual clinical environment now have proposed reference ranges. Our findings suggest that accommodation time, age, sex, or reproductive status do not influence the results derived from these recordings, indicating that this method is reliable for assessing the ANS function in small and medium-sized dog breeds.

Relationship between heart rate variability and carotid intima-media thickness in the Brazilian Longitudinal Study of Adult Health - ELSA-Brasil

BACKGROUND

Both increased carotid intima-media thickness (cIMT) and low heart rate variability (HRV) have been associated with cardiovascular mortality and morbidity. Thus, the aim of this study was to investigate whether cardio autonomic alterations are accompanied or not by subclinical atherosclerosis in participants of the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil).

METHODS

cIMT measures and 5-min HRV analyses were performed in apparently healthy adults. Heart rate variability was evaluated by linear time and frequency domain analyses. cIMT was defined as the average between the mean left and mean right cIMT values and was analysed as continuous and categorized variables (P≥75 or P<75). Multiple linear models using continuous variables and multivariate logistic regression with categorized cIMT and HRV quartiles were performed.

RESULTS

Out of 7256 participants eligible for analyses, 23·4% presented cIMT ≥ 75th percentile. Heart rate variability variables were reduced in cIMT ≥ P75 in comparison with cIMT < P75: SDNN 33·0 versus 37·0 ms, P<0·001; RMSSD 22·0 versus 26·0 ms, P<0·001; LF 191·0 versus 260·0 ms² , P<0·001; HF 164·0 versus 238·5 ms² , P<0·001. In crude analysis, an increased odds ratio for cIMT ≥ P75 was verified within the lowest two quartiles of LF and HF, but significances did not remain after adjustments for anthropometric and clinical variables.

CONCLUSIONS

Considering the entire sample, subjects with cIMT ≥ P75 presented lower HRV values, but no independent relationships were detected between cIMT and HRV after multivariate adjustment.

Does oxygen-enriched air better than normal air improve sympathovagal balance in recreational divers?An open-water study

Effects of the hyperbaric environment on the autonomic nervous system (ANS) in recreational divers are not firmly settled. Aim of this exploratory study was to (1) assess ANS changes during scuba diving via recordings of electrocardiograms (ECG) and to (2) study whether nitrox40 better improves sympathovagal balance over air. 13 experienced divers (~40yrs) performed two open-water dives each breathing either air or nitrox40 (25m/39min). 3-channel ECGs were recorded using a custom-made underwater Holter-monitor. The underwater Holter system proved to be safe. Air consumption exceeded nitrox40 consumption by 12% (n = 13; p < 0.05). Both air and nitrox40 dives reduced HR (10 vs 13%; p < 0.05). The overall HRV (pNN50: 82 vs 126%; p < 0.05) and its vagal proportion (RMSSD: 33 vs 50%; p < 0.05) increased during the dive. Moreover, low (LF: 61 vs 47%) and high (HF: 71 vs 140%) frequency power were increased (all p < 0.05), decreasing the ratio of LF to HF (22 vs 34%). : Conventional open-water dives distinctly affect the ANS in experienced recreational divers, with sympathetic activation less pronounced than vagal activation thereby improving the sympathovagal balance. Nitrox40 delivered two positive results: nitrox40 consumption was lower than air consumption, and nitrox40 better improved the sympathovagal balance over air.

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

AIM

To investigate whether heart rate variability (HRV) is a predictor for the incidence of diabetes in a 4-year follow-up.

MATERIALS AND METHODS

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 25^th percentile, between the 25^th and 75^th percentiles, and higher than the 75^th percentile. The association between HRV and diabetes incidence at 4-year follow-up was analysed using Poisson regression models with robust estimator.

RESULTS

Six hundred thirty-four participants (6.90%) developed diabetes within 4 years 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).

CONCLUSIONS

This study suggests that both overall variability and changes in parasympathetic modulation precede the incidence of diabetes. For four HRV indices below the 25^th 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.

Effects of ischaemic conditioning on tissue oxygen saturation and heart rate variability: an observational study

Objective

Ischaemic conditioning (IC) has organ-protective effects, but its clinical results have been inconsistent. Tissue oxygen saturation (StO₂) and heart rate variability (HRV) reflect peripheral microcirculation and autonomic nervous system activity, but their changes during IC have not been well documented. We assessed StO₂ and HRV during IC in patients undergoing cardiac surgery and healthy volunteers.

Methods

Ten patients undergoing cardiac surgery and 10 healthy male volunteers underwent remote IC (four 5-minute cycles of ischaemia/reperfusion) applied to the upper arm. Changes in StO₂ at the thenar eminence and HRV according to the R-R intervals were recorded during IC.

Results

The lowest StO₂ during ischaemia significantly decreased in patients and significantly increased in volunteers. Among the HRV parameters, the low-frequency domain, which corresponds to sympathetic activity, significantly increased after IC in volunteers but not in patients. Other variables were similar between the groups.

Conclusions

These results suggest that the minimum tissue oxygen content is depleted during ischaemia in patients and preserved in healthy volunteers. Sympathetic nervous activity seems to increase after IC in healthy volunteers but remains unaffected in patients. Thus, IC may act differently between patients undergoing cardiac surgery and healthy subjects.

Heart rate variability: are you using it properly? Standardisation checklist of procedures

BACKGROUND

Heart rate variability is used as an assessment method for cardiac autonomic modulation. Since the Task Force's publication on heart rate variability in 1996, the European Heart Rhythm Association Position Paper in 2015 and a recent publication in 2017, attention has been paid to recommendations on using heart rate variability analysis methods, as well as their applications in different physiological conditions and clinical studies. This analysis has proved to be useful as a complementary tool for clinical evaluation and to assess the effect of non-pharmacological therapeutic interventions, such as physical exercise programmes, on cardiac autonomic modulation.

OBJECTIVE

The aim of this article is to make recommendations and to develop a checklist of normalisation procedures regarding the use of heart rate variability data collection and analysis methodology, focusing on the cardiology area and cardiac rehabilitation.

METHODS

Based on previous heart rate variability publications, this paper provides a description of the most common shortcomings of using the analysis methods and considers recommendations and suggestions on how to minimise these occurrences by using a specific checklist.

CONCLUSIONS

This article includes recommendations and a checklist regarding the use of heart rate variability collection and analysis methods. This work could help improve reporting on clinical evaluation and therapeutic intervention results and consequently, disseminate heart rate variability knowledge.