Heart rate variability from short electrocardiographic recordings predicts mortality from all causes in middle-aged and elderly men. The Zutphen Study

The effect of reducing posttraumatic stress disorder symptoms on cardiovascular risk: Design and methodology of a randomized clinical trial

Posttraumatic stress disorder (PTSD) has been associated with accelerated progression of coronary heart disease (CHD). However, the underlying pathophysiological pathway has remained elusive and it is unclear whether there is a direct link between PTSD and CHD risk. This paper describes the methods of a randomized controlled trial developed to examine how changes in PTSD symptoms affect CHD disease pathways. One hundred twenty participants with current PTSD and who are free of known CHD will be randomized to receive either an evidence-based treatment for PTSD (Cognitive Processing Therapy; CPT) or a waitlist control (WL). Before and after CPT/WL, participants undergo assessment of CHD risk biomarkers reflecting autonomic nervous system dysregulation, systemic inflammation, and vascular endothelial dysfunction. The primary hypothesis is that individuals who show improvement in PTSD symptoms will show improvement in CHD risk biomarkers, whereas individuals who fail to improve or show worsening PTSD symptoms will have no change or worsening in CHD biomarkers. This study is expected to provide knowledge of the role of both the direct impact of PTSD symptoms on CHD risk pathways and the role of these systems as candidate mechanisms underlying the relationship between PTSD and CHD risk. Further, results will provide guidance on the utility of cognitive therapy as a tool to mitigate the accelerated progression of CHD in PTSD. Clinical Trials Registration: https://clinicaltrials.gov/ct2/show/NCT02736929; Unique identifier: NCT02736929.

Reduced vagal tone in women with endometriosis and auricular vagus nerve stimulation as a potential therapeutic approach

Sensory and sympathetic nerves have been shown to promote the progression of endometriosis through the release of neuromediators and the lesional activation of respective receptors. The role of vagus nerves (VN) in lesional progression, however, is completely unclear, despite the signs suggestive of increased sympathetic tone in women with endometriosis. This study was undertaken to investigate whether VN plays any role in the progression of endometriosis. We recruited 45 patients with endometriosis and 42 healthy women, who were given electrocardiogram test and their heart rate variability was evaluated. In addition, three prospective, and randomized mouse experiments were conducted that evaluated, respectively, the effect of vagotomy, the effect of VN stimulation (VNS), and the therapeutic potential of VNS after the endometriosis was well established. All lesions were excised, weighed, and processed for immunohistochemistry and histochemistry analysis of select markers for lesional progression and fibrosis. We found that endometriosis patients exhibited reduced vagal activity as compared with controls, indicative of disrupted autonomic balance. Vagotomy increased while VNS decreased the lesion weight as compared with control mice, concomitant with more progressive and retarded lesion development and fibrogenesis, respectively. In addition, VNS demonstrated promising therapeutic effect, as evidenced by significantly reduced lesion weight, more attenuated lesional progression concomitant with improved hyperalgesia. Taken together, our data indicate that VN activity may play a dampening role in the progression of endometriosis. Consequently, boosting the VN activity may have therapeutic potentials for patients with endometriosis.

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.

The Short-Term Effect of Occupational Levels of 50 Hz Electromagnetic Field on Human Heart Rate Variability

Previous studies have indicated that there is no consensus on the effects of extremely low-frequency electromagnetic (ELF-EMF) exposure on the cardiovascular system. This study aimed to explore the short-term effect of ELF-EMF exposure on heart rate (HR) and HR variability (HRV). The sample consisted of 34 healthy males aged 18-27 years. The participants were randomly assigned to the EMF (n = 17) or the Sham group (n = 17). We employed a double-blind repeated-measures design consisting of three 5 min experimental periods. The chest region of each individual in the EMF group was exposed to 50 Hz, 28 μT, linear polarized, continuous EMF during the EMF exposure period. HR and HRV data were recorded continuously by using a photoplethysmography sensor. Within-subject statistical analysis indicated a significant HR deceleration in both the EMF and Sham groups. However, the standard deviation of the NN intervals (SDNN), root mean square of successive differences (RMSSD), low-frequency (LF), and high-frequency (HF) powers increased only in the EMF group and remained stable in the Sham group. We also compared the same HRV indices measured during the EMF and Sham periods between the two experimental groups. The between-subject analysis results demonstrated significantly higher SDNN, RMSSD, LF, and HF values in the EMF group than in the Sham group. The LF/HF ratio did not change significantly within and between groups. On the basis of these results, we concluded that short-term exposure of the chest region to ELF-EMF could potentially enhance parasympathetic predominance during the resting condition. Bioelectromagnetics. 2021;42:60-75. © 2020 Bioelectromagnetics Society.

High-resolution, relational, resonance-based, electroencephalic mirroring (HIRREM) improves symptoms and autonomic function for insomnia: A randomized, placebo-controlled clinical trial

INTRODUCTION

Effective insomnia interventions that also address autonomic dysregulation are lacking. We evaluate high-resolution, relational, resonance-based, electroencephalic mirroring (HIRREM® ), in a randomized, controlled clinical trial. HIRREM is a noninvasive, closed-loop, allostatic, acoustic stimulation neurotechnology, to support self-optimization of brain rhythms.

METHODS

One hundred and seven adults (mean age 45.7, SD ± 5.6, 73 women), with Insomnia Severity Index (ISI) scores of ≥15, received ten, 90-min sessions of HIRREM, with tones linked to brainwaves (LB, 56), or random tones not linked to brainwaves (NL, 51), as an active, sham placebo. Outcomes were obtained at enrollment (V1), 1-7 days (V2), 8-10 weeks (V3), and 16-18 weeks (V4) after intervention. Primary outcome was differential change in ISI from V1 to V3. Secondary measures assessed depression (BDI), anxiety (BAI), quality of life (EQ-5D), and a sleep diary. Ten minute recordings of HR and BP allowed analysis of heart rate variability (HRV) and baroreflex sensitivity (BRS).

RESULTS

Of 107 randomized, 101 completed the intervention. Intention-to-treat analysis (107) of change from V1 to V3 revealed a mean reduction of ISI in NL of -4.93 (SE ± 0.76) points, with additional, significant reduction of -2.05 points (0.74) in LB (total reduction of -6.98, p = .045). Additional reduction of -2.30 points (0.76) was still present in the LB at V4 (p = .058). Total ISI reduction from V1 to V4 was -5.90 points for NL and -7.93 points in LB. There were group differences (p < .05) for multiple HRV and BRS measures (rMSSD, SDNN, HF alpha, and Seq ALL), as well as total sleep time, sleep onset latency, and sleep efficiency. There were no serious adverse events.

CONCLUSIONS

Results of this controlled clinical trial showed clinically relevant reduction of insomnia symptoms with HIRREM, over, and above an active, sham control, with associated, durable improvement in autonomic cardiovascular regulation.

Can Physical Activity While Sedentary Produce Health Benefits? A Single-Arm Randomized Trial

Background

Sedentary time poses a risk to health. Substituting physical activity for inactivity is obvious but this requires a behavior change. Interventions advocated to decrease uninterrupted physical inactivity (defined as Metabolic Equivalent of Task (METS) less than 1.5) are important. One such intervention is accomplished with the Gentle Jogger (GJ), a low risk motorized wellness device which produces effortless, rapid motion of the lower extremities simulating locomotion or fidgeting. GJ produces health benefits in type 2 diabetes, heart disease, and high blood pressure. The purpose of this trial was to ascertain whether GJ increases METS above 1.5 to explain its effectiveness despite sedentary behavior or whether tapping is responsible.

Methods

A randomized single-arm trial was conducted. Subjects were randomized to begin the study in either the supine or seated postures and on the same day crossed over with the starting posture reversed. Oxygen consumption was measured at rest and during GJ.

Results

Twenty-six subjects were studied (15 women and 11 men) with a mean age of 44 ± 15 years and BMI 27.9 ± 5.0, 19 were overweight or obese, and 7 had normal BMI. GJ increased oxygen consumption and METS 15% in the seated posture and 13% in the supine posture. No individual receiving GJ achieved METS exceeding 1.5.

Conclusions

In a moderately obese population, GJ in seated or supine posture did not exceed 1.5 METS. The values are comparable to those reported for sit-stand interventions and cannot explain the health benefits of GJ.

Trial registration

ClinicalTrials.gov, NCT03602365. Registered on July 26, 2018

Physiological Monitoring to Enhance Clinical Hypnosis and Psychotherapy

Physiological monitoring provides a useful access into the patient's affective state during hypnotically assisted therapeutic sessions. Physiological monitoring identifies autonomic dysregulation and can also display the process of restoring autonomic regulation via hypnosis and other quieting strategies. Commonly used modalities for physiological monitoring are identified, and clinical illustrations of how psychophysiological monitoring can be used in hypnosis and hypnotically assisted psychotherapy are provided. Clinicians may benefit from including psychophysiological knowledge in hypnosis education. Physiological monitoring may enhance hypnosis interventions for some disorders; however, more research is needed for evaluation of efficacy.

Optimal Continuous Positive Airway Pressure Treatment of Obstructive Sleep Apnea Reduces Daytime Resting Heart Rate in Prediabetes: A Randomized Controlled Study

Background It has been widely recognized that obstructive sleep apnea (OSA) is linked to cardiovascular disease. Yet, randomized controlled studies failed to demonstrate a clear cardiovascular benefit from OSA treatment, mainly because of poor adherence to continuous positive airway pressure (CPAP). To date, no prior study has assessed the effect of CPAP treatment on daytime resting heart rate, a strong predictor of adverse cardiovascular outcomes and mortality. Methods and Results We conducted a randomized controlled study in 39 participants with OSA and prediabetes, who received either in-laboratory all-night (ie, optimal) CPAP or an oral placebo for 2 weeks. During daytime, participants continued daily activities outside the laboratory. Resting heart rate was continuously assessed over 19 consecutive days and nights using an ambulatory device consisting of a single-lead ECG and triaxis accelerometer. Compared with placebo, CPAP reduced daytime resting heart rate (treatment difference, -4.1 beats/min; 95% CI, -6.5 to -1.7 beats/min; P=0.002). The magnitude of reduction in daytime resting heart rate after treatment significantly correlated with the magnitude of decrease in plasma norepinephrine, a marker of sympathetic activity (r=0.44; P=0.02), and the magnitude of decrease in OSA severity (ie, apnea-hypopnea index [r=0.48; P=0.005], oxygen desaturation index [r=0.50; P=0.003], and microarousal index [r=0.57; P<0.001]). Conclusions This proof-of-concept randomized controlled study demonstrates, for the first time, that CPAP treatment, when optimally used at night, reduces resting heart rate during the day, and therefore has positive cardiovascular carry over effects. These findings suggest that better identification and treatment of OSA may have important clinical implications for cardiovascular disease prevention. Registration URL: https:/// www.clini​caltr​ials.gov; Unique identifier: NCT01156116.

Early changes in ambulatory electrocardiography after transcatheter closure in patients with atrial septal defect and factors affecting heart rate variability

Background

Factors affecting heart rate variability (HRV) in patients with atrial septal defect (ASD) have not been clarified. This study sought to identify those factors and establish a preliminary risk model.

Methods

A total of 154 patients with ASD who underwent transcatheter closure and met the study requirements were analyzed in this study. Moreover, 26 patients with patent foramen ovale (PFO) were enrolled in our study as a control group. All patients underwent echocardiography and ambulatory electrocardiography before and one day after the procedure.

Results

The standard deviation of all normal-to-normal (NN) intervals (SDNN) and the standard deviation of the averages of the NN intervals in all 5 min segments of the entire recording (SDANN) were significantly higher and the heart rate was lower after closure than before closure in patients with ASD (SDNN: 6.08, 95% CI 3.00 to 9.15, p < 0.001; SDANN: 7.57, 95% CI 4.50 to 10.64, p < 0.001; heart rate: -1.17, 95% CI − 2.86 to − 0.48, p = 0.006). Multiple regression analyses indicated that age, sex, defect diameter, heart rate and diabetes were significantly associated with HRV indices (SDNN: R² = 0.415; P < 0.001). SDNN and SDANN had obvious correlations with right ventricular systolic pressure (SDNN: R = − 0.370, p < 0.001; SDANN: R = − 0.360, p < 0.001).

Conclusions

Factors affecting HRV in patients with ASD include age, sex, heart rate, defect size and diabetes. Furthermore, right ventricular systolic pressure plays an important role in the change in HRV.

Sex differences in cardiac vagal reactivation from the end of isometric handgrip exercise and at the onset of muscle metaboreflex isolation

A parasympathetic reactivation is an underlying mechanism mediating the rapid fall in heart rate (HR) at the onset of post-exercise ischemia (PEI) in humans. Herein, we tested the hypothesis that, compared to men, women present a slower HR recovery at the cessation of isometric handgrip exercise (i.e., onset of PEI) due to an attenuated cardiac vagal reactivation. Forty-seven (23 women) young and healthy volunteers were recruited. Subjects performed 90s of isometric handgrip exercise at 40% of maximal voluntary contraction followed by 3-min of PEI. The onset of PEI was analyzed over the first 30s in 10s windows. Cardiac vagal reactivation was indexed using the HR fall and by HR variability metrics (e.g., RMSSD and SDNN) immediately after the cessation of the exercise. HR was significantly increased from rest during exercise in men and women and increases were similar between sexes. However, following the cessation of exercise, the HR recovery was significantly slower in women compared to men regardless of the time point (women vs. men: ∆-14 ± 8 vs. ∆-18 ± 6 beats.min^-1 at 10s; ∆-20 ± 9 vs. ∆-25 ± 8 beats.min^-1 at 20s; ∆-22 ± 10 vs. ∆-27 ± 9 beats.min^-1 at 30s; P = .027). RMSSD and SDNN increased at the cessation of exercise in greater magnitude in men compared to women. These findings demonstrate that women had a slower HR recovery at the cessation of isometric handgrip exercise and onset of PEI compared to men, suggesting a sex-related difference in cardiac vagal reactivation in healthy young humans.

Snacking on Whole Almonds for Six Weeks Increases Heart Rate Variability during Mental Stress in Healthy Adults: A Randomized Controlled Trial

Cardiac autonomic regulation can be indirectly measured by heart rate variability (HRV). Low HRV, which can be induced by mental stress, is a predictor of risk of sudden cardiac death. Few studies have investigated cause-and-effect relationships between diet and HRV. Nut consumption is associated with CVD risk reduction, but the impact on HRV, particularly in response to stress, is unclear. Men and women (30–70 y) with above average risk of developing CVD were randomly assigned in a 6-week randomized, controlled, parallel arm trial to consume either whole almond or isocaloric control snacks (20% of daily estimated energy requirement). Control snacks contained the average nutrient profile of UK snacks. Five-minute periods of supine heart rate (HR) and HRV were measured at resting and during mental stress (Stroop color-word test) at baseline and six weeks. High frequency (HF) power, which reflects parasympathetic regulation of HR, was increased following almonds during the mental stress task relative to control (mean difference between groups 124 ms2; 95% CI 11, 237; p = 0.031, n = 105), but other indices were unaffected. Snacking on whole almonds instead of typical snacks may reduce risk of CVD partly by ameliorating the suppression of HRV during periods of mental stress.

Gender-Based Vegetarian and Nonvegetarian Dietary Impact on Cardiac Autonomic Function of Heart Rate Variability

Objective: Cardiovascular disease is one among the major mortality threats throughout the world. Autonomic activity of the nervous system can be examined by heart rate variability (HRV) analysis. Association of sympathetic and parasympathetic activities is directly related to HRV modulation. The aim of the study is to determine variations in HRV parameters among adult/adolescent male and female subjects due to vegetarian and nonvegetarian diet.Method: Ninety undergraduate students in each male and female group (N = 180) volunteered for the study. Based upon food habits, male and female subjects were categorized into four groups. Short-term (5-minute) heart rate recordings were measured from the subjects in a seated position before breakfast with minimum of 12 hours' fasting. Two-way analysis of variance was performed among the time and frequency domain variables.Results: Time domain variables are observed as significant (p < 0.05) between vegetarian males and females and also (p < 0.05) between male vegetarian and female nonvegetarians for standard deviation of NN intervals. Frequency domain HRV indices such as low frequency (LF; p = 0.01), high frequency (HF; p = 0.0001), and LF/HF (p < 0.001) resulted between male and female vegetarians. Significance of LF (p = 0.02), HF (p < 0.0001), and LF/HF (p < 0.01) was measured between male vegetarians and female nonvegetarians. LF (p = 0.02), HF (p = 0.04), and LF/HF (p = 0.002) resulted between nonvegetarian males and females. HF (p = 0.05) was enumerated between male vegetarians and nonvegetarians.Conclusions: Significant predominance of sympathetic cardiac activity was observed among male nonvegetarian consumers more than female vegetarians. Analysis demonstrates that the gender-based influence of vegetarian and nonvegetarian diet has significant correlation under HRV measurements.

Sleep heart rate variability assists the automatic prediction of long-term cardiovascular outcomes

OBJECTIVE

We aimed to investigate the association between sleep HRV and long-term cardiovascular disease (CVD) outcomes, and further explore whether HRV features can assist the automatic CVD prediction.

METHODS

We retrospectively analyzed polysomnography (PSG) data obtained from 2111 participants in the Sleep Heart Health Study, who were followed up for a median of 11.8 years after PSG acquisition. During follow-up, 1252 participants suffered CVD events (CVD group) and 859 participants remained CVD-free (non-CVD group). HRV measures, derived from time-domain and frequency-domain, were calculated. Regression models were created to determine the independent predictor for long-term CVD outcomes, and to explore the association between HRV and CVD latency. Furthermore, based on HRV and other clinical features, a model was trained to automatically predict CVD outcomes using the eXtreme Gradient Boosting algorithm.

RESULTS

Compared with the non-CVD group, decreased HRV during sleep was found in the CVD group. HRV, particularly its component of high frequency (HF), was demonstrated to be independent predictor of CVD outcomes. Moreover, normalized HF was positively correlated with CVD latency. The proposed prediction model achieved a total accuracy of 75.3%, in which sleep HRV features served as a supplement to the well-recognized CVD risk factors, such as aging, adiposity and sleep disorders.

CONCLUSIONS

Association between sleep HRV and long-term CVD outcomes was demonstrated here, suggesting that altered HRV during sleep might occur many years prior to the onset of CVD. Machine learning models, combining sleep HRV and other clinical characteristics, should be promising in the early prediction of CVD outcomes.

Effects of isometric handgrip training on cardiac autonomic profile: A systematic review and meta-analysis study

Meta-analyses have shown that isometric handgrip training reduces blood pressure in normotensive and hypertensive subjects. However, the effects on cardiac autonomic modulation are still controversial. Thus, the aim of this systematic review and meta-analysis was to analyse the effects of isometric handgrip training on cardiac autonomic modulation in normotensive and hypertensive subjects. For this, Medline, Cinhal, Embase, Spordiscus and PEdro were searched for relevant studies published until December 2018. Randomized controlled trials investigating the effect of isometric handgrip training on heart rate variability parameters were considered eligible. Parameters were obtained in time (standard deviation of all the RR intervals-SDNN, root mean square of successive differences between the normal adjacent RR intervals-RMSSD and the percentage of adjacent intervals with more than 50 ms-PNN50) and frequency domain (low frequency-LF, high frequency-HF and sympathovagal balance-LF/HF). Mean difference (MD) and 95% confidence interval (95% CI) were calculated using an inverse variance method with a random effects model. Seven trials were included in the systematic review and meta-analysis, totalling 86 participants. No significant effect was observed in heart rate variability parameters after isometric handgrip training (4 trials to SDNN: MD = -1.44 ms and 95% CI = -8.02, 5.14 ms; RMSSD: MD = -1.48 ms and 95% CI = -9.41, 6.45 ms; PNN50: MD = 0.85% and 95% CI = -1.10, 2.81%; 7 trials to LF: -0.17 n.u. and 95% CI = -6.32, 5.98 n.u.; HF: MD = 0.17 n.u. and 95% CI = -5.97, 6.30 n.u.; and LF/HF: MD = 0.13 and 95% CI = -0.34, 0.59). In conclusion, current literature indicates that isometric handgrip training does not improve heart rate variability.

Self-health monitoring and wearable neurotechnologies

Brain-computer interfaces and wearable neurotechnologies are now used to measure real-time neural and physiologic signals from the human body and hold immense potential for advancements in medical diagnostics, prevention, and intervention. Given the future role that wearable neurotechnologies will likely serve in the health sector, a critical state-of-the-art assessment is necessary to gain a better understanding of their current strengths and limitations. In this chapter we present wearable electroencephalography systems that reflect groundbreaking innovations and improvements in real-time data collection and health monitoring. We focus on specifications reflecting technical advantages and disadvantages, discuss their use in fundamental and clinical research, their current applications, limitations, and future directions. While many methodological and ethical challenges remain, these systems host the potential to facilitate large-scale data collection far beyond the reach of traditional research laboratory settings.

Heart and Brain Interaction of Psychiatric Illness: A Review Focused on Heart Rate Variability, Cognitive Function, and Quantitative Electroencephalography

Heart rate variability (HRV) reflects beat-to-beat variability in the heart rate due to the dynamic interplay of the sympathetic and parasympathetic nervous systems. HRV is considered an index of the functional status of the autonomic nervous system. A decrease in HRV is thus observed in individuals with autonomic dysfunction. Abnormal HRV has been reported in a range of mental disorders. In this review, we give an overview of HRV in patients with major depressive disorder (MDD), schizophrenia, and posttraumatic stress disorder (PTSD), one of whose core symptoms is cognitive dysfunction. The association between HRV and cognitive function is highlighted in this review. This review consists of three main sections. In the first section, we examine how HRV in patients with MDD, schizophrenia, and PTSD is characterized, and how it is different when compared to that in healthy controls. In the second section, beyond the heart itself, we discuss the intimate connection between the heart and the brain, focusing on how HRV interacts with quantitative electroencephalography (qEEG) in the context of physiological changes in the sleep cycle. Lastly, we finish the review with the examination of the association between HRV and cognitive function. The overall findings indicate that the reduction in HRV is one of main manifestations in MDD, schizophrenia, and PTSD, and also more generally HRV is closely linked to the change in qEEG and also to individual differences in cognitive performance.

First Evaluation of an Index of Low Vagally-Mediated Heart Rate Variability as a Marker of Health Risks in Human Adults: Proof of Concept

Multiple studies have demonstrated low vagally-mediated heart rate variability (HRV) being associated with a range of risk factors for heart disease and stroke, including inflammation, hyperglycemia, hyperlipidemia, and hypertension. Yet, no cut point exists that indicates elevated risk. In the present study we sought to identify a cut point-value for HRV that is associated with elevated risk across a range of known risk factors. Methods: A total of 9550 working adults from 19 study sites took part in a health assessment that included measures of inflammation, hyperglycemia, hyperlipidemia, and hypertension and vagally-mediated HRV (Root mean square of successive differences between normal heartbeats (RMSSD)). Multiple age and sex adjusted logistic regressions were calculated per risk factor (normal versus clinical range), with RMSSD being entered in binary at different cut points ranging from 15–39 msec with a 2 msec increment. Results: For daytime RMSSD, values below 25 ± 4 indicated elevated risk (odds ratios (OR) 1.5–3.5 across risk factors). For nighttime RMSSD, values below 29 ± 4 indicated elevated risk (OR 1.2–2.0). Conclusion: These results provide the first evidence that a single value of RMSSD may be associated with elevated risk across a range of established cardiovascular risk factors and may present an easy to assess novel marker of cardiovascular risk.

Global Sensitivity Analysis of a Cardiovascular Model for the Study of the Autonomic Response to Head-up Tilt Testing

This paper proposes the integration and analysis of a mathematical model representing the cardiovascular system and its short-term autonomic response to head-up tilt (HUT) testing. A Latin Hypercube Sampling method was applied to design an optimal experimental space, including 19 model parameters coming from the cardiovascular and baroreflex control systems. Then, a global, variance-based sensitivity analysis was applied to quantity the effects of these parameters on heart rate and systolic blood pressure. Results highlight the relevant influence of the intrinsic heart rate and the sympathetic and parasympathetic baroreflex gains on heart rate regulation, as well as the impact of left ventricle diastolic parameters on systolic blood pressure. Moreover, a significant effect of right ventricle dynamics on blood pressure was noted. These results provide valuable information for the application of such an integrated model for the analysis of the autonomic mechanisms regulating the cardiovascular response induced by postural changes. In particular, they suggest a convenient set of parameters to be identified in a subject-specific manner.

Negative Affect-Related Autonomic Arousal Mediates the Association between Baroreflex Dysfunction and Insulin Resistance in Non-Diabetic Young Adults

Autonomic dysfunction, in particular under-regulation of heart rate (HR) by the baroreflex, is implicated in development of insulin resistance (IR). According to reactivity hypothesis, sympathetic response to stressors may be more sensitive at predicting IR than baroreceptor sensitivity (BRS), a baseline measure of baroreflex functioning. Using ecological momentary assessment (EMA) of negative affect coupled with minute-to-minute HR and heart-rate variability (HRV) monitoring, we examined whether negative affect (NA)-related autonomic arousal mediates the association of BRS with IR. At baseline, BRS was measured, and fasting serum glucose and insulin levels were collected from 178 young adults (18-39 years old), from which homeostasis model assessment of IR (HOMA-IR) and beta-cell functioning (HOMA %B) were derived. Participants subsequently underwent one day of Holter HR and HRV monitoring while reporting negative affect levels via EMA. Multilevel modeling was used to assess the associations of momentary negative affect with HR and low- (LF) and high-frequency (HF) HRV during the 5-minute intervals following each EMA reading. Structural equation modeling was then used to determine whether individual differences in these associations mediated the association of BRS with IR, measured by HOMA-IR, HOMA %B, and insulin levels. As predicted, BRS was negatively associated with the IR (β = -.17, p = .024). However, NA-related autonomic arousal mediated their association, accounting for 56% of the covariance between BRS and IR. Not only do these results provide support for reactivity hypothesis, they reveal a potential point of intervention in the treatment of affective dysregulation.

Antenatal hemodynamic findings and heart rate variability in early school-age children born with fetal growth restriction

BACKGROUND

According to epidemiological studies, impaired intrauterine growth increases the risk for cardiovascular morbidity and mortality in adulthood. Heart rate variability (HRV), which reflects the autonomic nervous system function, has been used for risk assessment in adults while its dysfunction has been linked to poor cardiovascular outcome.

OBJECTIVE

We hypothesized that children who were born with fetal growth restriction (FGR) and antenatal blood flow redistribution have decreased HRV at early school age compared to their gestational age matched peers with normal intrauterine growth.

STUDY DESIGN

A prospectively collected cohort of children born with FGR (birth weight <10th percentile and/or abnormal umbilical artery flow, n = 28) underwent a 24-hour Holter monitoring at the mean age of 9 years and gestational age matched children with birth weight appropriate for gestational age (AGA, n = 19) served as controls. Time- and frequency domain HRV indices were measured and their associations with antenatal hemodynamic changes were analyzed.

RESULTS

Time- and frequency domain HRV parameters (standard deviation of R-R intervals, SDNN; low frequency, LF; high frequency, HF; LF/HF; very low frequency, VLF) did not differ significantly between FGR and AGA groups born between 24 and 40 weeks. Neither did they differ between children born with FGR and normal umbilical artery pulsatility or increased umbilical artery pulsatility. In total, 56% of the FGR children demonstrated blood flow redistribution (cerebroplacental ratio, CPR < -2 SD) during fetal life and their SDNN (p = .01), HF (p = .03) and VLF (p = .03) values were significantly lower than in FGR children with CPR ≥ -2SD.

CONCLUSIONS

Early school age children born with FGR and intrauterine blood flow redistribution demonstrated altered heart rate variability. These prenatal and postnatal findings may be helpful in targeting preventive cardiovascular measures in FGR.

Heritability and genetic correlations of heart rate variability at rest and during stress in the Oman Family Study

Supplemental Digital Content is available in the text

Introduction:

Individual differences in heart rate variability (HRV) can be partly attributed to genetic factors that may be more pronounced during stress. Using data from the Oman Family Study (OFS), we aimed to estimate and quantify the relative contribution of genes and environment to the variance of HRV at rest and during stress; calculate the overlap in genetic and environmental influences on HRV at rest and under stress using bivariate analyses of HRV parameters and heart rate (HR).

Methods:

Time and frequency domain HRV variables and average HR were measured from beat-to-beat HR obtained from electrocardiogram recordings at rest and during two stress tests [mental: Word Conflict Test (WCT) and physical: Cold Pressor Test (CPT)] in the OFS – a multigenerational pedigree consisting of five large Arab families with a total of 1326 participants. SOLAR software was used to perform quantitative genetic modelling.

Results:

Heritability estimates for HRV and HR ranged from 0.11 to 0.31 for rest, 0.09–0.43 for WCT, and 0.07–0.36 for CPT. A large part of the genetic influences during rest and stress conditions were shared with genetic correlations ranging between 0.52 and 0.86 for rest-WCT and 0.60–0.92 for rest-CPT. Nonetheless, genetic rest–stress correlations for most traits were significantly smaller than 1 indicating some stress-specific genetic effects.

Conclusion:

Genetic factors significantly influence HRV and HR at rest and under stress. Most of the genetic factors that influence HRV at rest also influence HRV during stress tests, although some unique genetic variance emerges during these challenging conditions.

Resting Heart Rate Variability Predicts Vulnerability to Pharmacologically-Induced Ventricular Arrhythmias in Male Rats

The electrical stability of the myocardium is dependent on the dynamic balance between sympathetic and parasympathetic influences on the heart, which is reflected by heart rate variability (HRV). Reduced HRV is a proposed predictor of sudden death caused by ventricular tachyarrhythmias in cardiac patients. However, the link between individual differences in HRV and ventricular tachyarrhythmic risk in populations without known pre-existing cardiac conditions is less well explored. In this study we investigated the extent to which individual differences in resting state HRV predict susceptibility to spontaneous and pharmacologically-induced ventricular arrhythmias in healthy rats. Radiotelemetric transmitters were implanted in 42 adult male Wild-type Groningen rats. ECG signals were recorded during 24-h resting conditions and under β-adrenoceptor pharmacological stimulation with isoproterenol and analyzed by means of time- and frequency-domain indexes of HRV. No significant association was found between individual differences in resting measures of HRV and spontaneous incidence of ventricular arrhythmias. However, lower resting values of HRV predicted a higher number of ventricular ectopic beats following β-adrenergic pharmacological stimulation with isoproterenol (0.02 mg/kg). Moreover, after isoproterenol administration, one rat with low resting HRV developed sustained ventricular tachycardia that led to death. The present results might be indicative of the potential utility of HRV measures of resting cardiac autonomic function for the prediction of ventricular arrhythmias, particularly during conditions of strong sympathetic activation, in populations without known cardiac disease.

A Copernican Approach to Brain Advancement: The Paradigm of Allostatic Orchestration

There are two main paradigms for brain-related science, with different implications for brain-focused intervention or advancement. The paradigm of homeostasis (“stability through constancy,” Walter Cannon), originating from laboratory-based experimental physiology pioneered by Claude Bernard, shows that living systems tend to maintain system functionality in the direction of constancy (or similitude). The aim of physiology is to elucidate the factors that maintain homeostasis, and therapeutics aim to correct abnormal factor functions. The homeostasis paradigm does not formally recognize influences outside its controlled experimental frames and it is variable in its modeling of neural contributions. The paradigm of allostatic orchestration (PAO) extends the principle of allostasis (“stability through change”) as originally put forth by Peter Sterling. The PAO originates from an evolutionary perspective and recognizes that biological set points change in anticipation of changing environments. The brain is the organ of central command, orchestrating cross-system operations to support optimal behavior at the level of the whole organism. Alternative views of blood pressure regulation and posttraumatic stress disorder (PTSD) illustrate differences between the paradigms. For the PAO, complexities of top-down neural effects and environmental context are foundational (not to be “factored out”), and anticipatory regulation is the principle of their interface. The allostatic state represents the integrated totality of brain-body interactions. Health itself is an allostatic state of optimal anticipatory oscillation, hypothesized to relate to the state of criticality, a mathematical point of poise between phases, on the border between order and disorder (or the “edge of chaos”). Diseases are allostatic states of impaired anticipatory oscillations, demonstrated as rigidifications of set points across the brain and body (disease comorbidity). Conciliation of the paradigms is possible, with “reactive homeostasis” resolved as an illusion stemming from the anticipation of environmental monotony. Considerations are presented with respect to implications of the two paradigms for brain-focused intervention or advancement; the hypothesis that the state of criticality is a vehicle for evolutionary processes; concordance with a philosophy of freedom based on ethical individualism as well as self-creativity, non-obsolescence, empowerment, and citizenship; and concluding reflections on the science and ethics of the placebo, and the potential for virtuous cycles of brain-Anthropocene interactions.

Should heart rate variability be "corrected" for heart rate? Biological, quantitative, and interpretive considerations

Metrics of heart period variability are widely used in the behavioral and biomedical sciences, although somewhat confusingly labeled as heart rate variability (HRV). Despite their wide use, HRV metrics are usually analyzed and interpreted without reference to prevailing levels of cardiac chronotropic state (i.e., mean heart rate or mean heart period). This isolated treatment of HRV metrics is nontrivial. All HRV metrics routinely used in the literature exhibit a known and positive relationship with the mean duration of the interval between two beats (heart period): as the heart period increases, so does its variability. This raises the question of whether HRV metrics should be "corrected" for the mean heart period (or its inverse, the heart rate). Here, we outline biological, quantitative, and interpretive issues engendered by this question. We provide arguments that HRV is neither uniformly nor simply a surrogate for heart period. We also identify knowledge gaps that remain to be satisfactorily addressed with respect to assumptions underlying existing HRV correction approaches. In doing so, we aim to stimulate further progress toward the rigorous use and disciplined interpretation of HRV. We close with provisional guidance on HRV reporting that acknowledges the complex interplay between the mean and variability of the heart period.

The Role of the Autonomic Nervous System on Cardiac Rhythm during the Evolution of Diabetes Mellitus Using Heart Rate Variability as a Biomarker

Heart rate variability (HRV) is highly influenced by the Autonomic Nervous System (ANS). Several illnesses have been associated with changes in the ANS, thus altering the pattern of HRV. However, the variability of the heart rhythm is originated within the Sinus Atrial Node (SAN) which has its own variability. Still, although both oscillators produce HRV, the influence of the SAN on HRV has not yet been exhaustively studied. On the other hand, the complications of diabetes mellitus (DM), for instance, nephropathy, retinopathy, and neuropathy, increase cardiovascular morbidity and mortality. Traditionally, these complications are diagnosed only when the patient is already suffering from the negative symptoms these complications implicate. Consequently, it is of paramount importance to develop new techniques for early diagnosis prior to any deterioration on healthy patients. HRV has been proved to be a valuable, noninvasive clinical evidence for evaluating diseases and even for describing aging and behavior. In this study, several ECGs were recorded and their RR and PP intervals were analyzed to detect the interpotential interval (ii) of the SAN. Additionally, HRV reduction was quantified to identify alterations in the nervous system within the nodal tissue via measuring the SD1/SD2 ratio in a Poincaré plot. With 15 years of DM development, the data showed an age-dependent increase in HRV due to the axon retraction of ANS neurons from its effectors. In addition, these alterations modify the heart rhythm-producing fatal arrhythmias. Therefore, it is possible to avoid the consequences of DM identifying alterations in SAN previous to its symptomatic appearance. This could be used as an early diagnosis indicator.

Presidential Address 2011: Autonomic modes of control and health

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

The Vagus Nerve Can Predict and Possibly Modulate Non-Communicable Chronic Diseases: Introducing a Neuroimmunological Paradigm to Public Health

Global burden of diseases (GBD) includes non-communicable conditions such as cardiovascular diseases, cancer and chronic obstructive pulmonary disease. These share important behavioral risk factors (e.g., smoking, diet) and pathophysiological contributing factors (oxidative stress, inflammation and excessive sympathetic activity). This article wishes to introduce to medicine and public health a new paradigm to predict, understand, prevent and possibly treat such diseases based on the science of neuro-immunology and specifically by focusing on vagal neuro-modulation. Vagal nerve activity is related to frontal brain activity which regulates unhealthy lifestyle behaviors. Epidemiologically, high vagal activity, indexed by greater heart rate variability (HRV), independently predicts reduced risk of GBD and better prognosis in GBD. Biologically, the vagus nerve inhibits oxidative stress, inflammation and sympathetic activity (and associated hypoxia). Finally, current non-invasive methods exist to activate this nerve for neuro-modulation, and have promising clinical effects. Indeed, preliminary evidence exists for the beneficial effects of vagal nerve activation in diabetes, stroke, myocardial infarction and possibly cancer. Thus, we propose to routinely implement measurement of HRV to predict such GBD in populations, and to test in randomized controlled trials effects of non-invasive vagal nerve activation on prevention and treatment of GBD, reflecting possible neuro-modulation of health.

Association between dysfunction of autonomic nervous system activity and mortality in schizophrenia

BACKGROUND

Patients with schizophrenia have a higher mortality risk than the general population. Additionally, the autonomic nervous system (ANS) activity of patients with schizophrenia is lower and more dysfunctional than that of the general population. Nonetheless, the association between ANS dysfunction and mortality in schizophrenia is unclear. The aim of this study was to investigate the association between ANS activity and mortality in schizophrenia and to evaluate the predictive values of heart rate variability for long-term survival.

METHODS

This study involves the 10-year follow-up of a sample population consisting of 59 Japanese inpatients with schizophrenia between 60 and 70 years of age from 2007 to 2016. The ANS activity of all patients was evaluated using heart rate variability in 2007.

RESULTS

Fifty-three participants could be followed up because they stayed in the hospital during the follow-up period. Of these patients, 11 died during follow-up. Their mean age at death was 70.55 ± 3.45 years. The parasympathetic activity of nonsurvivors was significantly lower than that of survivors, and multiple logistic regression analysis showed a significant association between death and parasympathetic activity.

CONCLUSION

We suggest that decreased parasympathetic activity could be associated with 10-year all-cause mortality in older schizophrenic patients.

Long-term treatment with supraphysiologic doses of levothyroxine in treatment-refractory mood disorders - A prospective study of cardiovascular tolerability

BACKGROUND

To investigate long-term effects of adjunctive prophylactic treatment with supraphysiologic doses of levothyroxine (L-T4) on cardiovascular tolerability in 23 patients with treatment-refractory mood disorders.

METHODS

Starting point for a comprehensive cardiovascular assessment in patients was the indication for long-term maintenance treatment with L-T4 (mean dose 463 mcg/day). Prospective longitudinal assessment of the cardiovascular risk profile included in addition to a physical examination and blood pressure measurement, several technical investigations: resting electrocardiogram, transthoracic echocardiogram, cardiac stress test, and holter electrocardiogram. Statistical analysis was performed by linear mixed effects models (LMM) for evaluation of longitudinal changes in various heart measures.

RESULTS

During the mean observational period of 20.4 months none of the heart measures reached statistical significance in change over time. None of the assessed cardiac parameters of each single patient was in a range predictive for cardiac dysfunction.

LIMITATIONS

Small sample size, no technical cardiac investigations prior to L-T4 initiation, no patient control group with mood disorders who did not receive L-T4.

CONCLUSIONS

Results of this study indicated no increased risk for cardiovascular disorders during treatment with supraphysiologic L-T4 doses in patients with refractory mood disorders.

Dysautonomia in Childhood Cancer Survivors: A Widely Underestimated Risk

PURPOSE

Survival rate of childhood cancers is now reaching 80% overall. However, early or late complications related to surgery, chemotherapy, and radiotherapy remain at a high rate and greatly increase the risk of late mortality. The objective of this study is to assess the autonomic nervous system (ANS) activity, measured through heart rate variability indices in childhood cancer survivors compared with healthy controls.

METHODS

This prospective study included 51 long-term childhood cancer survivors diagnosed before 15 years of age between 1987 and 1992 and controlled for age and sex with healthy volunteers.

RESULTS

We observed a significant increase in spontaneous heart rate (beats per minute) (67 ± 10 vs. 60 ± 10, p = 0.001), and all the studied parameters showed a significantly altered ANS activity in cases compared with healthy controls. In both groups, the main cofactors of dysautonomia (tobacco, drugs, cannabis, estro-progestative pills, alcohol, limited physical activity) were analyzed without any significant difference. The effect of cancer treatments received was not analyzed due to the small number of participants.

CONCLUSION

The results showed a significant ANS dysfunction in childhood cancer survivors compared with healthy controls and suggested the value of autonomic screening to underscore and possibly quantify the effect of the cancer treatments in a larger cohort. This evaluation could lead to the recommendation to increase physical activity, the most efficient way known to improve ANS activity, as already shown in other pathologies (breast cancer).

The Impact of Exercise in Rodent Models of Chronic Pain

PURPOSE OF REVIEW

Physical activity is increasingly recommended for chronic pain. In this review, we briefly survey recent, high-quality meta-analyses on the effects of exercise in human chronic pain populations, followed by a critical discussion of the rodent literature.

RECENT FINDINGS

Most meta-analytical studies on the effects of exercise in human chronic pain populations describe moderate improvements in various types of chronic pain, despite substantial variability in the outcomes reported in the primary literature. The most consistent findings suggest that while greater adherence to exercise programs produces better outcomes, there is minimal support for the superiority of one type of exercise over another. The rodent literature similarly suggests that while regular exercise reduces hypersensitivity in rodent models of chronic pain, exercise benefits do not appear to relate to either the type of injury or any particular facet of the exercise paradigm. Potential factors underlying these results are discussed, including the putative involvement of stress-induced analgesic effects associated with certain types of exercise paradigms. Exercise research using rodent models of chronic pain would benefit from increased attention to the role of stress in exercise-induced analgesia, as well as the incorporation of more clinically relevant exercise paradigms.

Assessment of Cardiac Autonomic Function in Relation to Methylmercury Neurotoxicity

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

Heart Rate Variability Moderates Challenge and Threat Reactivity to Sexism Among Women in STEM

Abstract. Using a biopsychosocial model of challenge and threat, we tested resting heart rate variability (HRV) as a moderator of physiological reactivity after experiencing sexism. Women science, technology, engineering, and mathematics (STEM) majors participated in a mock interview in which the male interviewer made a sexist or neutral comment. Resting HRV moderated physiological stress reactivity among women in the sexism condition, but not control, indicating lower resting HRV predicted greater physiological threat than challenge and higher resting HRV predicted greater physiological challenge than threat during the interview. These findings support the emotion regulation properties of HRV as applied to a biopsychosocial model of challenge and threat. Higher resting HRV may be adaptive for women experiencing sexism in male-dominated contexts like STEM.

Ultra-short-term heart rate variability during resistance exercise in the elderly

Despite the appeal of ultra-short-term heart rate variability (HRV) methods of analysis applied in the clinical and research settings, the number of studies that have investigated HRV by analyzing R-R interval (RRi) recordings shorter than 5 min is still limited. Moreover, ultra-short-term HRV analysis has not been extensively validated during exercise and, currently, no indications exist for its applicability during resistance exercise. The aim of the present study was to compare ultra-short-term HRV analysis with standard short-term HRV analysis during low-intensity, dynamic, lower limb resistance exercise in healthy elderly subjects. Heart rate (HR) and RRi signals were collected from 9 healthy elderly men during discontinuous incremental resistance exercise consisting of 4-min intervals at low intensities (10, 20, 30, and 35% of 1-repetition maximum). The original RRi signals were segmented into 1-, 2-, and 3-min sections. HRV was analyzed in the time domain (root mean square of the of differences between adjacent RRi, divided by the number of RRi, minus one [RMSSD]), RRi mean value and standard deviation [SDNN] (percentage of differences between adjacent NN intervals that are greater than 50 ms [pNN50]), and by non-linear analysis (short-term RRi standard deviation [SD1] and long-term RRi standard deviation [SD2]). No significant difference was found at any exercise intensity between the results of ultra-short-term HRV analysis and the results of standard short-term HRV analysis. Furthermore, we observed excellent (0.70 to 0.89) to near-perfect (0.90 to 1.00) concordance between linear and non-linear parameters calculated over 1- and 2-min signal sections and parameters calculated over 3-min signal sections. Ultra-short-term HRV analysis appears to be a reliable surrogate of standard short-term HRV analysis during resistance exercise in healthy elderly subjects.

Effects of whole-body vibration on heart rate variability: acute responses and training adaptations

Heart rate variability (HRV) is a noninvasive and practical measure of cardiac autonomic nervous system function, mainly the sympathetic and parasympathetic modulations of heart rate. A low HRV has been shown to be indicative of compromised cardiovascular health. Interventions that enhance HRV are therefore beneficial to cardiovascular health. Whole-body vibration (WBV) training has been proposed as an alternative time-efficient exercise intervention for the improvement of cardiovascular health. In this review, we discuss the effect of WBV both acute and after training on HRV. WBV training appears to be a useful therapeutic intervention to improve cardiac autonomic function in different populations, mainly through decreases in sympathovagal balance. Although the mechanisms by which WBV training improves symphathovagal balance are not yet well understood; enhancement of baroreflex sensitivity, nitric oxide bioavailability and angiotensin II levels seem to play an important role.

Enhanced Local Skeletal Muscle Oxidative Capacity and Microvascular Blood Flow Following 7-Day Ischemic Preconditioning in Healthy Humans

Ischemic preconditioning (IPC), which involves intermittent periods of ischemia followed by reperfusion, is an effective clinical intervention that reduces the risk of myocardial injury and confers ischemic tolerance to skeletal muscle. Repeated bouts of IPC have been shown to stimulate long-term changes vascular function, however, it is unclear what metabolic adaptations may occur locally in the muscle. Therefore, we investigated 7 days of bilateral lower limb IPC (4 × 5 min) above limb occlusion pressure (220 mmHg; n = 10), or sham (20 mmHg; n = 10), on local muscle oxidative capacity and microvascular blood flow. Oxidative capacity was measured using near-infrared spectroscopy (NIRS) during repeated short duration arterial occlusions (300 mmHg). Microvascular blood flow was assessed during the recovery from submaximal isometric plantar flexion exercises at 40 and 60% of maximal voluntary contraction (MVC). Following the intervention period, beyond the late phase of protection (72 h), muscle oxidative recovery kinetics were speeded by 13% (rate constant pre 2.89 ± 0.47 min^-1 vs. post 3.32 ± 0.69 min^-1; P < 0.05) and resting muscle oxygen consumption (mO₂) was reduced by 16.4% (pre 0.39 ± 0.16%.s^-1 vs. post 0.33 ± 0.14%.s^-1; P < 0.05). During exercise, changes in deoxygenated hemoglobin (HHb) from rest to steady state were reduced at 40 and 60% MVC (16 and 12%, respectively, P < 0.05) despite similar measures of total hemoglobin (tHb). At the cessation of exercise, the time constant for recovery in oxygenated hemoglobin (O₂Hb) was accelerated at 40 and 60% MVC (by 33 and 43%, respectively) suggesting enhanced reoxygenation in the muscle. No changes were reported for systemic measures of resting heart rate or blood pressure. In conclusion, repeated bouts of IPC over 7 consecutive days increased skeletal muscle oxidative capacity and microvascular muscle blood flow. These findings are consistent with enhanced mitochondrial and vascular function following repeated IPC and may be of clinical or sporting interest to enhance or offset reductions in muscle oxidative capacity.

The Relationship between a New Biomarker of Vagal Neuroimmunomodulation and Survival in Two Fatal Cancers

BACKGROUND

The vagus nerve may slow tumor progression because it inhibits inflammation. This study examined the relationship between a new vagal neuroimmunomodulation (NIM) index and survival in fatal cancers.

METHOD

We retroactively derived markers of vagal nerve activity indexed by heart rate variability (HRV), specifically the root mean square of successive differences (RMSSD), from patients' electrocardiograms near diagnosis. The NIM index was the ratio of RMSSD to C-reactive protein levels (RMSSD/CRP). Sample 1 included 202 Belgian patients with advanced pancreatic cancer (PC), while sample 2 included 71 Belgian patients with non-small cell lung cancer (NSCLC). In both samples, we examined the overall survival, while in sample 2, we additionally examined the survival time in deceased patients.

RESULTS

In PC patients, in a multivariate Cox regression controlling for confounders, the NIM index had a protective relative risk (RR) of 0.68 and 95% confidence interval (95% CI) of 0.51-0.92. In NSCLC patients, the NIM index also had a protective RR of 0.53 and 95% CI of 0.32-0.88. Finally, in NSCLC, patients with a higher NIM index survived more days (475.2) than those with lower NIM (285.1) (p < 0.05).

CONCLUSIONS

The NIM index, reflecting vagal modulation of inflammation, may be a new independent prognostic biomarker in fatal cancers.

Normal Values of Corrected Heart-Rate Variability in 10-Second Electrocardiograms for All Ages

Purpose: Heart-rate variability (HRV) measured on standard 10-s electrocardiograms (ECGs) has been associated with increased risk of cardiac and all-cause mortality, but age- and sex-dependent normal values have not been established. Since heart rate strongly affects HRV, its effect should be taken into account. We determined a comprehensive set of normal values of heart-rate corrected HRV derived from 10-s ECGs for both children and adults, covering both sexes.

Methods: Five population studies in the Netherlands (Pediatric Normal ECG Study, Leiden University Einthoven Science Project, Prevention of Renal and Vascular End-stage Disease Study, Utrecht Health Project, Rotterdam Study) provided 10-s, 12-lead ECGs. ECGs were stored digitally and analyzed by well-validated analysis software. We included cardiologically healthy participants, 42% being men. Their ages ranged from 11 days to 91 years. After quality control, 13,943 ECGs were available. Heart-rate correction formulas were derived using an exponential model. Two time-domain HRV markers were analyzed: the corrected standard deviation of the normal-to-normal RR intervals (SDNNc) and corrected root mean square of successive RR-interval differences (RMSSDc).

Results: There was a considerable age effect. For both SDNNc and RMSSDc, the median and the lower limit of normal decreased steadily from birth until old age. The upper limit of normal decreased until the age of 60, but increased markedly after that age. Differences of the median were minimal between men and women.

Conclusion: We report the first comprehensive set of normal values for heart-rate corrected 10-s HRV, which can be of value in clinical practice and in further research.

Improvements in Heart Rate Variability, Baroreflex Sensitivity, and Sleep After Use of Closed-Loop Allostatic Neurotechnology by a Heterogeneous Cohort

Background

Heart rate variability (HRV) is an indicator of dynamic adaptability of the autonomic nervous system. Few interventions target upstream, cerebral cortex components of the heart–brain system for autonomic management. We report changes in HRV and baroreflex sensitivity (BRS), associated with use of a noninvasive, closed-loop, allostatic, computer-guided, acoustic stimulation neurotechnology.

Methods

Over 5 years, 220 subjects with heterogeneous neurological, cardiovascular, and psychophysiological conditions consecutively enrolled in a naturalistic, single-arm study exploring clinical effects associated with use of the neurotechnology. Of those, 202 completed the study protocol and 160 had recordings adequate to analyze HRV and BRS. Mean age was 44.0 (SD 19.4), with 130 women. Participants received a mean of 16.1 (5.2) sessions, over 24.2 days (23.3), with 9.5 (3.8) actual intervention days. Sessions included real-time analysis of brain electrical activity and software algorithm-guided translation of selected frequencies into patterns of acoustic stimulation (audible tones of variable pitch and timing), to facilitate auto-calibration of neural oscillations. Outcomes including 10-min supine, at-rest recordings of blood pressure and heart rate, and inventories for insomnia (ISI) and depression (CES-D or BDI-II), were obtained at baseline and 15.3 (16.7) days after the last session.

Results

Compared to baseline, significant increases (all p < 0.001) were observed for measures of HRV across all participants including the mean percentage change for SDNN 24.2% (SE 0.04), and RMSSD, 42.2% (0.08), and BRS [Sequence Up, 55.5% (0.09), Sequence Down, 77.6% (0.23), and Sequence All, 53.7% (0.07)]. Significant improvements were noted in SAP, MAP, and DAP, as well as natural log of HF, and total power. Self-reported ISI was reduced (ISI, −6.4 points, SD 5.6, p < 0.001). The proportion reporting clinically significant depressive symptoms reduced from 48.2% at baseline to 22.1% at follow-up. Linear regression showed that rightward asymmetry predicted lower SDNN (p = 0.02). Exploratory analysis showed a trend for improved balance of temporal lobe high-frequency amplitudes over the course of initial sessions.

Conclusion

These findings indicate that use of a noninvasive, allostatic, closed-loop neurotechnology appears to have robust potential for public health efforts to support greater flexibility in autonomic cardiovascular regulation, through self-optimization of electrical activity at the level of the brain.

Reprint of: Marine OMEGA-3 fatty acids in the prevention of cardiovascular disease

Omega-6 (ω6) and omega-3 (ω3) fatty acids are two classes of dietary polyunsaturated fatty acids derived from linoleic acid (18:2ω6) and α-linolenic acid (18:3ω3), respectively. Enzymatic metabolism of linoleic and α-linolenic acids generates arachidonic acid (20:4ω6) and eicosapentaenoic acid (20:5ω3; EPA), respectively, both of which are substrates for enzymes that yield eicosanoids with multiple and varying physiological functions. Further elongation and desaturation of EPA yields the 22-carbon fatty acid docosahexaenoic acid (22:6ω3; DHA). The main dietary source of EPA and DHA for human consumption is fish, especially oily fish. There is considerable evidence that EPA and DHA are protective against cardiovascular disease (heart disease and stroke), particularly in individuals with pre-existing disease. ω3 Fatty acids benefit multiple risk factors including blood pressure, blood vessel function, heart function and blood lipids, and they have antithrombotic, anti-inflammatory and anti-oxidative actions. ω3 Fatty acids do not adversely interact with medications. Supplementation with ω3 fatty acids is recommended in individuals with elevated blood triglyceride levels and patients with coronary heart disease. A practical recommendation for the general population is to increase ω3 fatty acid intake by incorporating fish as part of a healthy diet that includes increased fruits and vegetables, and moderation of salt intake. Health authorities recommend the general population should consume at least two oily fish meals per week.

Heart Rate Variability following Combined Aerobic and Resistance Training in Sedentary Hypertensive Women: A Randomised Control Trial

Objective

To investigate the effect of combined aerobic and resistance training (CART) on heart rate variability in sedentary, hypertensive women.

Participants

A total of twenty-eight hypertensive (Stage 1 and 2) sedentary women (Age 40.54 ± 4.2 yrs; Height 155.14 ± 5.4 cm; Weight 70.96 ± 10.2 kg; BMI 29.6 ± 4.4; Duration of HTN: 6.43 ± 2.5 yrs) were recruited for the study.

Methods

Participants were randomly assigned to either the CART group that performed combined aerobic and resistance exercise of moderate intensity [aerobic exercise 50–80% of HR_max (maximum heart rate) and resistance exercises at 50–80% of 1 Repetition Maximum (RM)], 5 times/week for 4 weeks, or to the control group that followed conventional treatment without any supervised exercise intervention.

Main outcome measures

Resting blood pressure was measured and standard heart rate variability (HRV) indices were calculated using time domain (SDNN, pNN50, RMSSD) and frequency domain (LFnu, HFnu, LF/HF and TP) analysis.

Results

CART group demonstrated an increase in HFnu, TP, SDNN, and RMSSD, (p < 0.05) along with a significant decrease in LFnu, LF/HF ratio, systolic blood pressure, and diastolic blood pressure (p < 0.05).

Conclusion

CART showed significant improvement in HRV parameters indicating vagal dominance in middle-aged hypertensive women. Therefore, exercise training in combined form (aerobic and resistance) may be incorporated in the management programs of the patients suffering from hypertension in order to augment improvement in their cardiac autonomic control.

Building Resilience in an Urban Police Department

OBJECTIVE

The aim of this study is to examine a resilience training intervention that impacts autonomic responses to stress and improves cardiovascular risk, psychological, and physiological outcomes in police.

METHODS

Officers [(n = 38) 22 to 54 years] modified emotional and physical responses to stress using self-regulation. Measurements include psychological and physiological measures [eg, heart rate variability (HRV), blood pressure, C-reactive protein)] obtained at three time intervals.

RESULTS

Age was significantly (P < 0.05) associated with changes on several measures of psychological stress (eg, critical incident stress, emotional vitality, and depression). Associations were found between coherence and improved HbA1c (r = -0.66, P < 0.001) and stress due to organizational pressures (r = -0.44, P = 0.03). Improvements in sympathetic and parasympathetic contributors of HRV were significant (P < 0.03).

CONCLUSION

A stress-resilience intervention improves certain responses to job stress with greater benefits for younger participants.

Heart Rate Variability: An Old Metric with New Meaning in the Era of Using mHealth technologies for Health and Exercise Training Guidance. Part Two: Prognosis and Training

It has been demonstrated that heart rate variability (HRV) is predictive of all-cause and cardiovascular mortality using clinical ECG recordings. This is true for rest, exercise and ambulatory HRV clinical ECG device recordings in prospective cohorts. Recently, there has been a rapid increase in the use of mobile health technologies (mHealth) and commercial wearable fitness devices. Most of these devices use ECG or photo-based plethysmography and both are validated for providing accurate heart rate measurements. This offers the opportunity to make risk information from HRV more widely available. The physiology of HRV and the available technology by which it can be assessed has been summarised in Part 1 of this review. In Part 2 the association between HRV and risk stratification is addressed by reviewing the current evidence from data acquired by resting ECG, exercise ECG and medical ambulatory devices. This is followed by a discussion of the use of HRV to guide the training of athletes and as a part of fitness programmes.

Exercise training and cardiac autonomic function in type 2 diabetes mellitus: A systematic review

Cardiac autonomic neuropathy (CAN) is a common complication of type 2 diabetes mellitus (T2DM). It has been found to independently predict all cause and cardiovascular disease (CVD) mortality. It remains unclear whether exercise training could improve autonomic control in T2DM patients. The purpose of this study was to systematically review the effects of exercise training on cardiac autonomic function in T2DM patients. Electronic databases (MEDLINE, CENTRAL, PEDro, Scopus and Web of science) were systematically searched to retrieve relevant evidence. Clinical trials administering exercise training for at least 4 weeks and examining either heart rate variability (HRV), baroreflex sensitivity (BRS), heart rate recovery (HRR) as outcome measures were eligible. Eighteen articles were found to be relevant and were then assessed for characteristics and quality. Fifteen studies out of 18 found that exercise training leads to positive improvements in autonomic function of T2DM patients. Exercise participation enhances cardiac autonomic function of type 2 diabetics and therefore should be implemented in their management programs.

Successful use of closed-loop allostatic neurotechnology for post-traumatic stress symptoms in military personnel: self-reported and autonomic improvements

BACKGROUND

Military-related post-traumatic stress (PTS) is associated with numerous symptom clusters and diminished autonomic cardiovascular regulation. High-resolution, relational, resonance-based, electroencephalic mirroring (HIRREM®) is a noninvasive, closed-loop, allostatic, acoustic stimulation neurotechnology that produces real-time translation of dominant brain frequencies into audible tones of variable pitch and timing to support the auto-calibration of neural oscillations. We report clinical, autonomic, and functional effects after the use of HIRREM® for symptoms of military-related PTS.

METHODS

Eighteen service members or recent veterans (15 active-duty, 3 veterans, most from special operations, 1 female), with a mean age of 40.9 (SD = 6.9) years and symptoms of PTS lasting from 1 to 25 years, undertook 19.5 (SD = 1.1) sessions over 12 days. Inventories for symptoms of PTS (Posttraumatic Stress Disorder Checklist - Military version, PCL-M), insomnia (Insomnia Severity Index, ISI), depression (Center for Epidemiologic Studies Depression Scale, CES-D), and anxiety (Generalized Anxiety Disorder 7-item scale, GAD-7) were collected before (Visit 1, V1), immediately after (Visit 2, V2), and at 1 month (Visit 3, V3), 3 (Visit 4, V4), and 6 (Visit 5, V5) months after intervention completion. Other measures only taken at V1 and V2 included blood pressure and heart rate recordings to analyze heart rate variability (HRV) and baroreflex sensitivity (BRS), functional performance (reaction and grip strength) testing, blood and saliva for biomarkers of stress and inflammation, and blood for epigenetic testing. Paired t-tests, Wilcoxon signed-rank tests, and a repeated-measures ANOVA were performed.

RESULTS

Clinically relevant, significant reductions in all symptom scores were observed at V2, with durability through V5. There were significant improvements in multiple measures of HRV and BRS [Standard deviation of the normal beat to normal beat interval (SDNN), root mean square of the successive differences (rMSSD), high frequency (HF), low frequency (LF), and total power, HF alpha, sequence all, and systolic, diastolic and mean arterial pressure] as well as reaction testing. Trends were seen for improved grip strength and a reduction in C-Reactive Protein (CRP), Angiotensin II to Angiotensin 1-7 ratio and Interleukin-10, with no change in DNA n-methylation. There were no dropouts or adverse events reported.

CONCLUSIONS

Service members or veterans showed reductions in symptomatology of PTS, insomnia, depressive mood, and anxiety that were durable through 6 months after the use of a closed-loop allostatic neurotechnology for the auto-calibration of neural oscillations. This study is the first to report increased HRV or BRS after the use of an intervention for service members or veterans with PTS. Ongoing investigations are strongly warranted.

TRIAL REGISTRATION

NCT03230890 , retrospectively registered July 25, 2017.

Stochastic Pacing Inhibits Spatially Discordant Cardiac Alternans

Depressed heart rate variability is a well-established risk factor for sudden cardiac death in survivors of acute myocardial infarction and for those with congestive heart failure. Although measurements of heart rate variability provide a valuable prognostic tool, it is unclear whether reduced heart rate variability itself is proarrhythmic or if it simply correlates with the severity of autonomic nervous system dysfunction. In this work, we investigate a possible mechanism by which heart rate variability could protect against cardiac arrhythmia. Specifically, in numerical simulations, we observe an inverse relationship between the variance of stochastic pacing and the occurrence of spatially discordant alternans, an arrhythmia that is widely believed to facilitate the development of cardiac fibrillation. By analyzing the effects of conduction velocity restitution, cellular dynamics, electrotonic coupling, and stochastic pacing on the nodal dynamics of spatially discordant alternans, we provide intuition for this observed behavior and propose control strategies to inhibit discordant alternans.