Autonomic regulation of the heart rate in humans under conditions of acute experimental hypoxia

Autonomic regulation of the heart rate (HR) was studied in young healthy volunteers under conditions of experimental acute normobaric hypoxia. Spectral analysis of the HR variability (HRV) was performed with differential sphygmography. The total spectral power (TP) of the HRV and its low and high frequency components (LF and HF, respectively) were assessed, and the sympathovagal balance (LFn/HFn) was calculated. Acute hypoxia increased the sympathetic and decreased the parasympathetic effects on the heart and was accompanied in the majority of subjects by a significant increase in HR and a decrease in HRV. The change in the autonomic regulation of the cardiac rhythm was assumed to be a mechanism of heart activity adaptation to acute hypoxia.Translated from Fiziologiya Cheloveka, Vol. 31, No. 1, 2005, pp. 82–87.Original Russian Text Copyright © 2005 by Nesterov.     

Seasonal Changes in Heart Rate Variability in 11- to 13-Year-Old Girls

Heart rate variability (HRV) was assessed each quarter during a year in 11- to 13-year-old girls with a Valenta medical diagnostic system. The HRV was highest in winter and lowest in summer (in 12-year-old girls) and autumn (in 11- and 13-year-old girls), indicating seasonal changes in the degree of β-adrenergic effects on the heart (lowest in winter and highest in summer and/or autumn). The changes were most pronounced in 11-year-old girls, i.e., at the onset of puberty. Seasonal changes in the HRV can be explained by changes in the blood levels of direct and indirect endogenous modulators of chemoresponsiveness and are considered to be a mechanism of human adaptation to external conditions.__________Translated from Fiziologiya Cheloveka, Vol. 31, No. 4, 2005, pp. 43–49.Original Russian Text Copyright © 2005 by Kaisina, Sizova, Tsirkin, Trukhina.     

Mechanisms of Periodic Heart Rate Oscillations: A Study Using Controlled Breathing Tests

An orthostatic test with frequency-controlled breathing (with periods of 4, 6, 8, 10, and 12 s) was used to analyze frequency estimates of the heart rate variability (HRV) spectrum in the low frequency (LF) and high frequency (HF) ranges in 36 volunteers (26 men and 10 women) aged 19–21 years without signs of heart or respiratory pathology. The subjects took a breath at the moment of an auditory signal. There were no other requirements for the respiration rhythm. Variables were compared using Wilcoxon’s test for pairwise comparisons; correlations were estimated by Spearman’s rank correlation R test. The sensitivities of the LF and HF ranges of the HRV spectrum to periodic respiratory perturbations at different frequencies were demonstrated to differ from each other. Autonomous 0.10- and 0.25-Hz circuits of oscillatory processes were found in HRV. The transition zone of influence of these circuits was located in the region around 0.125 Hz. The characteristics of the 0.10- and 0.25-Hz oscillations in HRV were studied. It was demonstrated that the 0.10-Hz oscillatory process is a potent mechanism of heart rate control, is affected by external factors, and determines the dynamics of the autonomic nervous state of the body, while the 0.25-Hz process is a regulatory mechanism of medium strength, is resistant to external factors, and characterizes the adaptation reserve of the autonomic nervous control of the heart rate, as well as the autonomic nervous state of the body. Resonance responses in the HRV spec-trum can be used for studying the characteristics of the 0.10- and 0.25-Hz oscillations.__________Translated from Fiziologiya Cheloveka, Vol. 31, No. 3, 2005, pp. 76–83.Original Russian Text Copyright © 2005 by Kiselev, Kirichuk, Posnenkova, Gridnev.     

Effects of Heart Rate Variability Biofeedback in Subjects with Stress-Related Chronic Neck Pain: A Pilot Study

Recent studies focusing on autonomic nervous system (ANS) dysfunctions, together with theoretical pathophysiological models of musculoskeletal disorders, indicate the involvement of ANS regulation in development and maintenance of chronic muscle pain. Research has demonstrated the effectiveness of heart rate variability (HRV) biofeedback (BF) in increasing HRV and reducing the symptoms of different disorders characterized by ANS aberration. The study investigated the effects of resonance frequency HRV BF on autonomic regulation and perceived health, pain, stress and disability in 24 subjects with stress-related chronic neck-shoulder pain. Twelve subjects participated in 10 weekly sessions of resonant HRV BF and were compared to a control group. Subjective reports and HRV measures during relaxation and in response to a standardized stress protocol were assessed for both groups pre- and post-intervention. Group × time interactions revealed a significantly stronger increase over time in perceived health (SF-36) for the treatment group, including vitality, bodily pain and social functioning. Interactions were also seen for HRV during relaxation and reactivity to stress. The present pilot study indicates improvement in perceived health over a 10 week intervention with HRV-biofeedback in subjects with chronic neck-pain. Increased resting HRV as well as enhanced reactivity to hand grip and cold pressor tests might reflect beneficial effects on ANS regulation, and suggest that this intervention protocol is suitable for a larger controlled trial.     

A Pilot Study on the Effects of Heart Rate Variability Biofeedback in Patients with Depression and in Healthy Subjects

Decreased vagal activity and increased sympathetic arousal have been proposed as major contributors to the increased risk of cardiovascular mortality in patients with depression. It was aim of the present study to assess the feasibility of using heart rate variability (HRV) biofeedback to treat moderate to severe depression. This was an open-label study in which 14 patients with different degrees of depression (13 f, 1 m) aged 30 years (18–47; median; range) and 12 healthy volunteers attended 6 sessions of HRV biofeedback over two weeks. Another 12 healthy subjects were observed under an active control condition. At follow up BDI was found significantly decreased (BDI 6; 2–20; median 25%–75% quartile) as compared to baseline conditions (BDI 22;15–29) in patients with depression. In addition, depressed patients had reduced anxiety, decreased heart rate and increased HRV after conduction of biofeedback (p < 0.05). By contrast, no changes were noted in healthy subjects receiving biofeedback nor in normal controls. In conclusion, HRV biofeedback appears to be a useful adjunct for the treatment of depression, associated with increases in HRV.     

A Pilot Study of the Efficacy of Heart Rate Variability (HRV) Biofeedback in Patients with Fibromyalgia

Fibromyalgia (FM) is a non-inflammatory rheumatologic disorder characterized by musculoskeletal pain, fatigue, depression, cognitive dysfunction and sleep disturbance. Research suggests that autonomic dysfunction may account for some of the symptomatology of FM. An open label trial of biofeedback training was conducted to manipulate suboptimal heart rate variability (HRV), a key marker of autonomic dysfunction. Methods: Twelve women ages 18–60 with FM completed 10 weekly sessions of HRV biofeedback. They were taught to breathe at their resonant frequency (RF) and asked to practice twice daily. At sessions 1, 10 and 3-month follow-up, physiological and questionnaire data were collected. Results: There were clinically significant decreases in depression and pain and improvement in functioning from Session 1 to a 3-month follow-up. For depression, the improvement occurred by Session 10. HRV and blood pressure variability (BPV) increased during biofeedback tasks. HRV increased from Sessions 1–10, while BPV decreased from Session 1 to the 3 month follow-up. Conclusions: These data suggest that HRV biofeedback may be a useful treatment for FM, perhaps mediated by autonomic changes. While HRV effects were immediate, blood pressure, baroreflex, and therapeutic effects were delayed. This is consistent with data on the relationship among stress, HPA axis activity, and brain function.     

Peak High-Frequency HRV and Peak Alpha Frequency Higher in PTSD

Posttraumatic stress disorder (PTSD) is difficult to treat and current PTSD treatments are not effective for all people. Despite limited evidence for its efficacy, some clinicians have implemented biofeedback for PTSD treatment. As a first step in constructing an effective biofeedback treatment program, we assessed respiration, electroencephalography (EEG) and heart rate variability (HRV) as potential biofeedback parameters for a future clinical trial. This cross-sectional study included 86 veterans; 59 with and 27 without PTSD. Data were collected on EEG measures, HRV, and respiration rate during an attentive resting state. Measures were analyzed to assess sensitivity to PTSD status and the relationship to PTSD symptoms. Peak alpha frequency was higher in the PTSD group (F(1,84) = 6.14, p = 0.01). Peak high-frequency HRV was lower in the PTSD group (F(2,78) = 26.5, p < 0.00005) when adjusting for respiration rate. All other EEG and HRV measures and respiration were not different between groups. Peak high-frequency HRV and peak alpha frequency are sensitive to PTSD status and may be potential biofeedback parameters for future PTSD clinical trials.     

Voluntarily Produced Increases in Heart Rate Variability Modulate Autonomic Effects of Endotoxin Induced Systemic Inflammation: An Exploratory Study

Exposure of healthy people to lipopolysaccharide (LPS; endotoxin) produces a pro-inflammatory response, subjective symptoms, and decreased heart rate variability (HRV). Given the efficacy of HRV biofeedback (BF) for treating asthma, the large autonomic effects of HRV BF, and the link between vagus nerve activity and inflammation, we hypothesized that HRV BF would dampen the acute manifestations of systemic inflammation induced by LPS challenge. Healthy participants age 18-40 were randomly assigned to four-one-hour training sessions of either HRV BF (n = 6) or a control 15/min paced breathing condition (n = 5) prior to acute experimentally induced LPS exposure. Participants were coached to do the procedures for 10 min each at five hourly time points after LPS injection, and then 2 h later. Subjective symptoms, HRV parameters, and plasma cytokine levels were measured at each time point, 2 h afterward, and the following morning. Participants were able to perform the procedures both during four pre-exposure training sessions and while experiencing LPS-induced symptoms. The HRV BF group showed significant attenuation of the LPS-induced decline in HRV for the 6 h following LPS exposure, suggesting that HRV BF decreased autonomic dysfunction produced by LPS-induced inflammation. HRV BF also reduced symptoms of headache and eye sensitivity to light, but did not affect LPS-induced levels of pro-inflammatory cytokines or symptoms of nausea, muscle aches, or feverishness. Further evaluation of HRV BF appears to be warranted among patients with inflammatory conditions.     

Continuous Multi-Parameter Heart Rate Variability Analysis Heralds Onset of Sepsis in Adults

Background

Early diagnosis of sepsis enables timely resuscitation and antibiotics and prevents subsequent morbidity and mortality. Clinical approaches relying on point-in-time analysis of vital signs or lab values are often insensitive, non-specific and late diagnostic markers of sepsis. Exploring otherwise hidden information within intervals-in-time, heart rate variability (HRV) has been documented to be both altered in the presence of sepsis, and correlated with its severity. We hypothesized that by continuously tracking individual patient HRV over time in patients as they develop sepsis, we would demonstrate reduced HRV in association with the onset of sepsis.

Methodology/Principal Findings

We monitored heart rate continuously in adult bone marrow transplant (BMT) patients (n = 21) beginning a day before their BMT and continuing until recovery or withdrawal (12±4 days). We characterized HRV continuously over time with a panel of time, frequency, complexity, and scale-invariant domain techniques. We defined baseline HRV as mean variability for the first 24 h of monitoring and studied individual and population average percentage change (from baseline) over time in diverse HRV metrics, in comparison with the time of clinical diagnosis and treatment of sepsis (defined as systemic inflammatory response syndrome along with clinically suspected infection requiring treatment). Of the 21 patients enrolled, 4 patients withdrew, leaving 17 patients who completed the study. Fourteen patients developed sepsis requiring antibiotic therapy, whereas 3 did not. On average, for 12 out of 14 infected patients, a significant (25%) reduction prior to the clinical diagnosis and treatment of sepsis was observed in standard deviation, root mean square successive difference, sample and multiscale entropy, fast Fourier transform, detrended fluctuation analysis, and wavelet variability metrics. For infected patients (n = 14), wavelet HRV demonstrated a 25% drop from baseline 35 h prior to sepsis on average. For 3 out of 3 non-infected patients, all measures, except root mean square successive difference and entropy, showed no significant reduction. Significant correlation was present amongst these HRV metrics for the entire population.

Conclusions/Significance

Continuous HRV monitoring is feasible in ambulatory patients, demonstrates significant HRV alteration in individual patients in association with, and prior to clinical diagnosis and treatment of sepsis, and merits further investigation as a means of providing early warning of sepsis.     

Link between Peripheral Artery Disease and Heart Rate Variability in Hemodialysis Patients

Peripheral artery disease (PAD) and low heart rate variability (HRV) are highly prevalent in hemodialysis patients, and both are associated with increased cardiovascular morbidity and mortality. This study aims to examine the suggested relationship between PAD and HRV, and the relationship of parameters before and after hemodialysis. This study enrolled 161 maintenance hemodialysis patients. PAD was defined as ABI < 0.9 in either leg. HRV was performed to assess changes before and after hemodialysis. The change in HRV (△HRV) was defined as post-hemodialysis HRV minus pre-hemodialysis HRV. Patients’ clinical parameters were collected from the dialysis records. All HRV parameters except high frequency (HF) % were lower in patients with PAD than patients without PAD, though not achieving significant level. In patients without PAD, HF (P = 0.013), low frequency (LF) % (P = 0.028) and LF/HF (P = 0.034) were significantly elevated after hemodialysis, whereas no significant HRV parameters change was noted in patients with PAD. Serum intact parathyroid hormone was independently associated with △HF (β = -0.970, P = 0.032) and △LF% (β = -12.609, P = 0.049). Uric acid level (β = -0.154, P = 0.027) was negatively associated with △LF/HF in patients without PAD. Our results demonstrated that some of the HRV parameters were significantly increased after hemodialysis in patients without PAD, but not in patients with PAD, reflecting a state of impaired sympatho-vagal equilibrium. Severity of secondary hyperparathyroidism and hyperuricemia contributed to lesser HRV parameters increase after hemodialysis in patients without PAD.     

Towards meeting Tinbergen's challenge

In mammals, sex specialization is reflected by differences in brain anatomy and function. Measurable differences are documented in reproductive behavior, cognition, and emotion. We hypothesized that gonadotropin-releasing hormone (GnRH) plays a crucial role in controlling the extent of the brain's sex specificity and that changes in GnRH action during critical periods of brain development, such as puberty, will result in altered sex-specific behavioral and physiological patterns. We blocked puberty in half of the 48 same-sex Scottish mule Texel cross sheep twins with GnRH analog (GnRHa) goserelin acetate every 3 weeks, beginning just before puberty. To determine the effects of GnRHa treatment on sex-specific behavior and emotion regulation in different social contexts, we employed the food acquisition task (FAT) and measurement of heart rate variability (HRV). ANOVA revealed significant sex and sex × treatment interaction effects, suggesting that treated males were more likely to leave their companions to acquire food than untreated, while the opposite effect was observed in females. Concordant results were seen in HRV; treated males displayed higher HRV than untreated, while the reverse pattern was found in females, as shown by significant sex and sex × treatment interaction effects. We conclude that long-term prepubertal GnRHa treatment significantly affected sex-specific brain development, which impacted emotion and behavior regulation in sheep. These results suggest that GnRH is a modulator of cognitive function in the developing brain and that the sexes are differentially affected by GnRH modulation.     

A Pilot Study of Brief Heart Rate Variability Biofeedback to Reduce Craving in Young Adult Men Receiving Inpatient Treatment for Substance Use Disorders

The present pilot study investigated the implementation feasibility, and efficacy for reducing alcohol and drug craving, of a brief, 3-session heart rate variability biofeedback (HRV BFB) intervention added to a traditional 28-day substance abuse disorder inpatient treatment program. Forty-eight young adult men received either treatment as usual (TAU) plus three sessions of HRV BFB training over 3 weeks, or TAU only. Participants receiving HRV BFB training were instructed to practice daily using a hand-held HRV BFB device. HRV BFB training was well tolerated by participants and supported by treatment staff. Men receiving TAU + HRV BFB demonstrated a greater, medium effect size reduction in alcohol and drug craving compared to those receiving TAU only, although this difference did not reach statistical significance. In addition, an interaction effect was observed in analyses that accounted for baseline craving levels, wherein heart rate variability (HRV) levels at treatment entry were predictive of changes in craving in the TAU group only. Low baseline levels of HRV were associated with increases in craving, whereas higher baseline HRV levels were associated with greater decreases in craving from start to end of treatment. In the TAU + HRV BFB group, however, there was no such association. That is, HRV BFB appeared to dissociate individual differences in baseline HRV levels from changes in craving. Given that alcohol and drug craving often precipitates relapse, HRV BFB merits further study as an adjunct treatment to ameliorate craving experienced by persons with substance use disorders.     

Response to Rhinovirus Infection by Human Airway Epithelial Cells and Peripheral Blood Mononuclear Cells in an In Vitro Two-Chamber Tissue Culture System

Human rhinovirus (HRV) infections are associated with the common cold, occasionally with more serious lower respiratory tract illnesses, and frequently with asthma exacerbations. The clinical features of HRV infection and its association with asthma exacerbation suggest that some HRV disease results from virus-induced host immune responses to infection. To study the HRV-infection-induced host responses and the contribution of these responses to disease, we have developed an in vitro model of HRV infection of human airway epithelial cells (Calu-3 cells) and subsequent exposure of human peripheral blood mononuclear cells (PBMCs) to these infected cells in a two-chamber trans-well tissue culture system. Using this model, we studied HRV 14 (species B) and HRV 16 (species A) induced cytokine and chemokine responses with PBMCs from four healthy adults. Infection of Calu-3 cells with either virus induced HRV-associated increases in FGF-Basic, IL-15, IL-6, IL-28A, ENA-78 and IP-10. The addition of PBMCs to HRV 14-infected cells gave significant increases in MIP-1β, IL-28A, MCP-2, and IFN-α as compared with mock-infected cells. Interestingly, ENA-78 levels were reduced in HRV 14 infected cells that were exposed to PBMCs. Addition of PBMCs to HRV 16-infected cells did not induce MIP-1β, IL-28A and IFN-α efficiently nor did it decrease ENA-78 levels. Our results demonstrate a clear difference between HRV 14 and HRV 16 and the source of PBMCs, in up or down regulation of several cytokines including those that are linked to airway inflammation. Such differences might be one of the reasons for variation in disease associated with different HRV species including variation in their link to asthma exacerbations as suggested by other studies. Further study of immune responses associated with different HRVs and PBMCs from different patient groups, and the mechanisms leading to these differences, should help characterize pathogenesis of HRV disease and generate novel approaches to its treatment.     

The Effect of Biofeedback on Function in Patients with Heart Failure

Decreased HRV has been consistently associated with increased cardiac mortality and morbidity in HF patients. The aim of this study is to determine if a 6-week course of heart rate variability (HRV) biofeedback and breathing retraining could increase exercise tolerance, HRV, and quality of life in patients with New York Heart Association Class I-III heart failure (HF). Participants (N = 29) were randomly assigned to either the treatment group consisting of six sessions of breathing retraining, HRV biofeedback and daily practice, or the comparison group consisting of six sessions of quasi-false alpha-theta biofeedback and daily practice. Exercise tolerance, measured by the 6-min walk test (6MWT), HRV, measured by the standard deviation of normal of normal beats (SDNN), and quality of life, measured by the Minnesota Living with Congestive Heart Failure Questionnaire, were measured baseline (week 0), post (week 6), and follow-up (week 18). Cardiorespiratory biofeedback significantly increased exercise tolerance (p = .05) for the treatment group in the high (≥31%) left ventricular ejection fraction (LVEF) category between baseline and follow-up. Neither a significant difference in SDNN (p = .09) nor quality of life (p = .08), was found between baseline and follow-up. A combination of HRV biofeedback and breathing retraining may improve exercise tolerance in patients with HF with an LVEF of 31% or higher. Because exercise tolerance is considered a strong prognostic indicator, cardiorespiratory biofeedback has the potential to improve cardiac mortality and morbidity in HF patients.

Electrochemical detection of nucleic base mismatches with ferrocenyl naphthalene diimide

Electrochemical detection of nucleic base mismatches was attempted successfully with ferrocenyl naphthalene diimide (FND) in a model system with 20-meric double-stranded oligonucleotides with or without a mismatch(es). Thus, dA(20) or a 20-meric sequence of the lac Z gene was immobilized on a gold electrode and complementary oligonucleotides with different numbers of mismatches were allowed to hybridize in the presence of FND to give rise to an electrochemical signal. The signal intensity varied depending on the number of unpaired bases on the DNA duplex. From experiments with a quartz crystal microbalance, eight molecules of FND were found to bind to the 20-meric double-stranded oligos and this number decreased as the number of mismatches increased. These findings were further supported by matrix-assisted laser desorption ionization time-of-flight mass spectroscopy. This novel method will be useful for the analysis of single-nucleotide polymorphisms present on human genes.     

Short-Term Heart Rate Variability—Influence of Gender and Age in Healthy Subjects

In the recent years, short-term heart rate variability (HRV) describing complex variations of beat-to-beat interval series that are mainly controlled by the autonomic nervous system (ANS) has been increasingly analyzed to assess the ANS activity in different diseases and under various conditions. In contrast to long-term HRV analysis, short-term investigations (<30 min) provide a test result almost immediately. Thus, short-term HRV analysis is suitable for ambulatory care, patient monitoring and all those applications where the result is urgently needed. In a previous study, we could show significant variations of 5-min HRV indices according to age in almost all domains (linear and nonlinear) in 1906 healthy subjects from the KORA S4 cohort. Based on the same group of subjects, general gender-related influences on HRV indices are to be determined in this study. Short-term 5-min HRV indices from linear time and frequency domain and from nonlinear methods (compression entropy, detrended fluctuation analysis, traditional and segmented Poincaré plot analysis, irreversibility analysis, symbolic dynamics, correlation and mutual information analysis) were determined from 782 females and 1124 males. First, we examined the gender differences in two age clusters (25–49 years and 50–74 years). Secondly, we investigated the gender-specific development of HRV indices in five age decade categories, namely for ages 25–34, 35–44, 45–54, 55–64 and 65–74 years. In this study, significant modifications of the indices according to gender could be obtained, especially in the frequency domain and correlation analyses. Furthermore, there were significant modifications according to age in nearly all of the domains. The gender differences disappeared within the last two age decades and the age dependencies disappeared in the last decade. To summarize gender and age influences need to be considered when performing HRV studies even if these influences only partly differ.     

Heart rate variability and methylphenidate in children with ADHD

Although an extensive number of studies support the efficacy and tolerability of stimulants in the treatment of attention deficit/hyperactivity disorder (ADHD), in recent years, increasing concerns have been raised about their cardiovascular safety. We investigated whether a time domain analysis of heart rate variability (HRV) recordings in 24-h ECG under medication with stimulants yielded new information about therapy control in ADHD. We analysed the HRV parameter standard deviation of all normal sinus RR intervals over 24 h (SDNN), percentage of successive normal sinus RR intervals > 50 ms (pNN50) and root-mean-square of the successive normal sinus RR interval difference (rMSSD) from 23 children diagnosed by ADHD (19 boys and 4 girls), aged 10.5 ± 2.2 years, who were consecutively referred to our outpatient clinic for paediatric cardiology. Eleven children received medication with methylphenidate (MPH), while twelve children were initially examined without medication. Of these, eight probands were re-examined after therapy with MPH was established. Controls comprised 19 children (10 boys, 9 girls) from our Holter ECG data base without any cardiac or circulatory disease. Compared to healthy controls, the ADHD children with and without MPH treatment showed significantly higher mean heart rates (ADHD without MPH: 94.3 ± 2.2; ADHD with MPH: 90.5 ± 1.8, controls: 84.7 ± 1.8). pNN50 (ADHD without MPH: 6.5 ± 2.7; ADHD with MPH: 14.2 ± 6.9, controls: 21.5 ± 9.0) and rMSSD (ADHD without MPH: 26.1 ± 4.1; ADHD with MPH: 36.7 ± 8.3, controls: 44.5 ± 10.1) were lowest in ADHD children without MPH, middle in ADHD children with MPH and highest in controls. SDNN values were not significantly different. The hourly analysis shows highly significant reduced pNN50 and rMSSD values in untreated ADHD children between 5:00 pm and 6:00 am while the pattern approaches to levels of controls during MPH treatment. Data of this pilot study indicate a decreased vagal tone with significantly diminished HRV and higher heart rates in unmedicated ADHD children. These parameters of autonomic activation are ameliorated by MPH treatment. No evidence for negative impact of MPH on HRV was detected. Further studies will clarify a potential cardio-protective effect of MPH in ADHD.     

Heart Rate Variability (HRV) and Posttraumatic Stress Disorder (PTSD): A Pilot Study

Exposure to combat experiences is associated with increased risk of developing Post Traumatic Stress Disorder. Prolonged exposure therapy and cognitive processing therapy have garnered a significant amount of empirical support for PTSD treatment; however, they are not universally effective with some patients continuing to struggle with residual PTSD symptoms. Heart rate variability (HRV) is a measure of the autonomic nervous system functioning and reflects an individual’s ability to adaptively cope with stress. A pilot study was undertaken to determine if veterans with PTSD (as measured by the Clinician-Administered PTSD Scale and the PTSD Checklist) would show significantly different HRV prior to an intervention at baseline compared to controls; specifically, to determine whether the HRV among veterans with PTSD is more depressed than that among veterans without PTSD. The study also aimed at assessing the feasibility, acceptability, and potential efficacy of providing HRV biofeedback as a treatment for PTSD. The findings suggest that implementing an HRV biofeedback as a treatment for PTSD is effective, feasible, and acceptable for veterans. Veterans with combat-related PTSD displayed significantly depressed HRV as compared to subjects without PTSD. When the veterans with PTSD were randomly assigned to receive either HRV biofeedback plus treatment as usual (TAU) or just TAU, the results indicated that HRV biofeedback significantly increased the HRV while reducing symptoms of PTSD. However, the TAU had no significant effect on either HRV or symptom reduction. A larger randomized control trial to validate these findings appears warranted.     

Heart rate variability as a marker of cardiovascular dysautonomia in post-COVID-19 syndrome using artificial intelligence

IntroductionCardiovascular dysautonomia comprising postural orthostatic tachycardia syndrome (POTS) and orthostatic hypotension (OH) is one of the presentations in COVID-19 recovered subjects. We aim to determine the prevalence of cardiovascular dysautonomia in post COVID-19 patients and to evaluate an Artificial Intelligence (AI) model to identify time domain heart rate variability (HRV) measures most suitable for short term ECG in these subjects.MethodsThis observational study enrolled 92 recently COVID-19 recovered subjects who underwent measurement of heart rate and blood pressure response to standing up from supine position and a 12-lead ECG recording for 60 s period during supine paced breathing. Using feature extraction, ECG features including those of HRV (RMSSD and SDNN) were obtained. An AI model was constructed with ShAP AI interpretability to determine time domain HRV features representing post COVID-19 recovered state. In addition, 120 healthy volunteers were enrolled as controls.ResultsCardiovascular dysautonomia was present in 15.21% (OH:13.04%; POTS:2.17%). Patients with OH had significantly lower HRV and higher inflammatory markers. HRV (RMSSD) was significantly lower in post COVID-19 patients compared to healthy controls (13.9 ± 11.8 ms vs 19.9 ± 19.5 ms; P = 0.01) with inverse correlation between HRV and inflammatory markers. Multiple perceptron was best performing AI model with HRV(RMSSD) being the top time domain HRV feature distinguishing between COVID-19 recovered patients and healthy controls.ConclusionPresent study showed that cardiovascular dysautonomia is common in COVID-19 recovered subjects with a significantly lower HRV compared to healthy controls. The AI model was able to distinguish between COVID-19 recovered patients and healthy controls.     

The Effects of Respiratory Sinus Arrhythmia Biofeedback on Heart Rate Variability and Posttraumatic Stress Disorder Symptoms: A Pilot Study

Recent studies have found a significant association between PTSD and low heart rate variability (HRV), a biomarker of autonomic dysregulation. Research indicates that respiratory sinus arrhythmia (RSA) biofeedback increases HRV while reducing related pathological symptoms. This controlled pilot study compared RSA biofeedback to progressive muscle relaxation (PMR) as adjunctive interventions for 38 persons with PTSD symptoms in a residential treatment facility for a substance use disorder. Both groups were assessed at pre-intervention and 4-week post-intervention. Group × time interactions revealed significantly greater reductions in depressive symptoms and increases in HRV indices for the RSA group. Both groups significantly reduced PTSD and insomnia symptoms and a statistical trend was observed for reduced substance craving for the RSA group. Increases in HRV were significantly associated with PTSD symptom reduction. Overall, these results provide preliminary support for the efficacy of RSA biofeedback in improving physiological and psychological health for individuals with PTSD.