The Influence of Heart Rate Variability Biofeedback on Cardiac Regulation and Functional Brain Connectivity

Unraveling the temporal interplay of slow-paced breathing and prefrontal transcranial direct current stimulation on cardiac indices of autonomic activity

The neurovisceral integration model proposes that information flows bidirectionally between the brain and the heart via the vagus nerve, indexed by vagally mediated heart rate variability (vmHRV). Voluntary reduction in breathing rate (slow-paced breathing, SPB, 5.5 Breathing Per Minute (BPM)) can enhance vmHRV. Additionally, prefrontal transcranial direct current stimulation (tDCS) can modulate the excitability of the prefrontal region and influence the vagus nerve. However, research on the combination of SPB and prefrontal tDCS to increase vmHRV and other cardiac (heart rate (HR) and blood pressure) and peripheral (skin conductance) indices is scarce. We hypothesized that the combination of 20 min of SPB and prefrontal tDCS would have a greater effect than each intervention in isolation. Hence, 200 participants were divided into four groups: active tDCS with SPB, active tDCS with 15 BPM breathing, sham tDCS with SPB, and sham tDCS with 15 BPM breathing. Regardless of the tDCS condition, the 5.5 BPM group showed a significant increase in vmHRV over 20 minutes and significant decreases in HR at the first and second 5-min epochs of the intervention. Regardless of breathing condition, the active tDCS group exhibited higher HR at the fourth 5-min epoch of the intervention than the sham tDCS group. No other effects were observed. Overall, SPB is a robust technique for increasing vmHRV, whereas prefrontal tDCS may produce effects that counteract those of SPB. More research is necessary to test whether and how SPB and neuromodulation approaches can be combined to improve cardiac vagal tone.

Can HRV Biofeedback Training Improve the Mental Resilience of Icelandic Police Officers?

High heart rate variability (HRV) is increasingly recognized as an indicator of a healthy regulatory system, reflecting the dynamic balance between sympathetic (SNS) and parasympathetic (PSNS) nervous system activity. According to the neurovisceral integration model, this balance is managed by the central autonomic network (CAN), comprised of specific brain regions involved in emotional, attentional, and autonomic regulation. HRV thus reflects the performance of the cognitive, affective, and autonomic regulation system. Numerous studies support the relationship between HRV and the CAN, including research on HRV biofeedback training (HRVBF). Studies on the effectiveness of HRVBF for professions such as police officers have shown improvements in self-regulation, decision-making, and performance. However, few studies have specifically explored HRVBF's influence on HRV metrics in police officers, highlighting a need for further research. This study addresses this gap by randomly assigning 27 Icelandic police officers to intervention or wait-list control groups. The intervention group underwent a five-week HRVBF program, including group and individual training sessions. Results showed significant increases in HRV metrics for the intervention group, indicating improved autonomic function and stress resilience. Mental resilience increased significantly as measured by subjective measures of attentional control, mindful awareness, and reduced fatigue. These findings support the efficacy of HRVBF in enhancing HRV and mental resilience for police officers, suggesting its applicability and potential for integration into existing training programs.

Relationship between central autonomic effective connectivity and heart rate variability: A Resting-state fMRI dynamic causal modeling study

The central autonomic network (CAN) serves as a regulatory hub with top-down regulatory control and integration of bottom-up physiological feedback via the autonomic nervous system. Heart rate variability (HRV)-the time variance of the heart's beat-to-beat intervals-is an index of the CAN's affective and behavioral regulatory capacity. Although neural functional connectivities that are associated with HRV and CAN have been well studied, no published report to date has studied effective (directional) connectivities (EC) that are associated with HRV and CAN. Better understanding of neural EC in the brain has the potential to improve our understanding of how the CAN sub-regions regulate HRV. To begin to address this knowledge gap, we employed resting-state functional magnetic resonance imaging and dynamic causal modeling (DCM) with parametric empirical Bayes analyses in 34 healthy adults (19 females; mean age= 32.68 years [SD= 14.09], age range 18-68 years) to examine the bottom-up and top-down neural circuits associated with HRV. Throughout the whole brain, we identified 12 regions associated with HRV. DCM analyses revealed that the ECs from the right amygdala to the anterior cingulate cortex and to the ventrolateral prefrontal cortex had a negative linear relationship with HRV and a positive linear relationship with heart rate. These findings suggest that ECs from the amygdala to the prefrontal cortex may represent a neural circuit associated with regulation of cardiodynamics.

Heart Rate Variability During Rapid Eye Movement Sleep is Associated with Reduced Negative Memory Bias

Emotional memories change over time, but the mechanisms supporting this change are not well understood. Sleep has been identified as one mechanism that supports memory consolidation, with sleep selectively benefitting negative emotional consolidation at the expense of neutral memories, with specific oscillatory events linked to this process. In contrast, the consolidation of neutral and positive memories, compared to negative memories, has been associated with increased vagally-mediated vagal heart rate variability (HRV) during wakefulness. However, how HRV during sleep contributes to emotional memory consolidation remains unexplored. We investigated how sleep oscillations and vagal contributions during sleep contribute to the consolidation of neutral and negative memories. Using a double-blind, placebo-controlled, within-subject, cross-over design, we examined the impact of pharmacological vagal suppression using zolpidem on overnight emotional memory consolidation. Thirty-two participants encoded neutral and negative pictures in the morning, followed by picture recognition tests before and after a night of sleep. Zolpidem or placebo was administered in the evening before overnight sleep, and participants were monitored with electroencephalography and electrocardiography. In the placebo condition, greater overnight improvement for neutral pictures was associated with higher vagal HRV in both Non-Rapid Eye Movement Slow Wave Sleep (NREM SWS) and REM. Additionally, the emotional memory tradeoff (i.e., difference between consolidation of neutral versus negative memories) was associated with higher vagal HRV during REM, but in this case, neutral memories were remembered better than negative memories, indicating a potential role for REM vagal HRV in promoting a positive memory bias overnight. Zolpidem, on the other hand, reduced vagal HRV during SWS, increased NREM sigma power, and eliminated the positive memory bias. Lastly, we used a stepwise linear mixed effects regression to determine how NREM sigma power and vagal HRV during REM independently explained the variance in the emotional memory tradeoff effect. We found that the addition of vagal HRV in combination with sleep significantly improved the model's fit. Overall, our results suggest that sleep brain oscillations and vagal signals synergistically interact in the overnight consolidation of emotional memories, with REM vagal HRV critically contributing to the positive memory bias.

Exploring Heart Rate Variability Biofeedback as a Nonpharmacological Intervention for Enhancing Perioperative Care: A Narrative Review

Heart rate variability biofeedback (HRVBF) is a non-invasive therapeutic technique that aims to regulate variability in heart rate. This intervention has promise in mitigating perioperative stress, a critical factor for surgical patient outcomes. This comprehensive review aimed to explore the current evidence on the perioperative role of HRV biofeedback in improving patient outcomes, reducing perioperative stress, enhancing recovery, and optimizing anaesthesia management. A review of the PubMed and Google Scholar databases was conducted to identify articles focused on HRVBF in relation to the perioperative period. Studies were selected using appropriate keywords in English (MeSH). Ample potential applications of HRVBF in clinical anaesthesia have been identified and proven feasible. It is a non-invasive and an easy method an anaesthesiologists has at its disposal with potential utility in reducing perioperative stress, as a tool of optimization of comorbidities, analgesia supplementation and in predicting catastrophic complications. Although HRVBF has the potential to enhance anaesthesia management and improve patient outcomes, several limitations and challenges must be addressed to maximize its clinical utility. Overcoming these obstacles through research and technological advancements will be crucial for realizing the full benefits of HRVBF in perioperative care.

The Physiological and Clinical-Behavioral Effects of Heart Rate Variability Biofeedback in Adolescents with Autism: A Pilot Randomized Controlled Trial

Adolescents with autism present lower levels of cardiac vagal modulation. It was hypothesized that Heart Rate Variability Biofeedback (HRVB) increases cardiac vagal modulation in adolescents with autism, resulting in positive effects on physiological and psychosocial parameters. It was also hypothesized that home-based HRVB training is feasible. In a single-blind, randomized sham-controlled pilot trial, adolescents with autism performed supervised HRVB (n = 24) or sham training (n = 20). Subsequently, half of the adolescents received HRVB training at home, whereas the other subset did not practice. Physiological, cortisol and behavioral data were collected during stress-provoking assessments before and after each training period. Supervised HRVB resulted in a late increase in cardiac vagal modulation in adolescents with autism. Heart rate increased and cortisol decreased significantly immediately after supervised HRVB, but none of these effects remained after follow-up. Following supervised HRVB, no significant change in psychosocial functioning was found. Home-based HRVB was feasible, adolescents reported lower symptoms of stress, but a significant decrease in compliance rate was found. HRVB is feasible and effective in adolescents with autism given the late-emerging increases in cardiac vagal modulation and decrease in stress symptoms. Replicating this study with a larger sample and further exploration of the working mechanisms of HRVB are recommended. ClinicalTrials.gov , NCT04628715.

Heart Rate Variability Biofeedback Intervention Programme to Improve Attention in Primary Schools

The importance of attentional capacity for academic performance is highlighted by the increasing demands placed on students during primary school. Between the ages of 7 and 12, there is an evolutionary improvement in attentional capacity and the school environment is considered an appropriate setting in which to develop programmes to improve attention. Heart rate variability is an appropriate indicator of attentional capacity. For all these reasons, a heart rate variability biofeedback intervention focused on breathing was developed and implemented to improve attention. The intervention consisted of two phases. In the first phase, the school teachers were trained to develop the intervention; in the second, students received five individual sessions from their teachers. In each individual session, they learned to breathe to increase their heart rate variability. A total of 272 girls and 314 boys (N = 586) aged 7-12 years participated in the programme. To study the impact of the intervention on three primary school age groups, the attention of Control and Experimental groups was assessed before and after the implementation of the programme. According to the data obtained, despite developmental improvements, the students who participated in the programme showed an increase in heart rate variability and an improvement in attentional capacity, with a greater impact on the first cycle of primary school. The usefulness of heart rate variability biofeedback interventions in improving attention in primary school is discussed and arguments for their use in children are presented.

Effects of Ten Biofeedback Sessions on Athletes' Physiological, Psychological, and Cognitive Functioning: A Randomized Controlled Trial with International Tennis Players

Our aim in this study was to test the effect of 10 sessions of biofeedback (BFB) on physiological, psychological, and cognitive functioning of international tennis players. In this randomized controlled trial, we recruited 16 international tennis players (11 male, 5 female; Mage = 17.31, SD = 0.87 years), who were randomly assigned to either an intervention group (IG; n = 8) or a control group (CG; n = 8). Those in the IG received 10 multimodal BFB sessions over four weeks, while those in the CG received no intervention. We assessed physiological, psychological, and cognitive parameters before and after the intervention and found a positive effect for skin temperature, state anxiety, and cognitive performance in the IG versus the CG. We provide preliminary data that 10 sessions of multimodal BFB improved cognitive functions and reduced anxiety symptoms in international tennis players. Future investigators should consider increasing sample size, incorporating an active CG, and studying these effects across diverse athletic disciplines.

Eight-week stress management exercise program improves mental health and autonomic nervous system of adults exposed to chronic stress

BACKGROUND

This study investigated a stress management exercise program's effect on mental health, muscle pain, and autonomic nervous system activity in adults exposed to chronic stress.

METHODS

Thirty mothers between 40 to 59 years old raising children with disabilities were equally allocated into the yoga (YG) or control group (CG). The YG participated in 16 prop-assisted yoga sessions twice weekly for eight weeks, focusing on relaxing and strengthening neck, shoulder, back, and waist stress-related muscles. The Beck Depression Inventory, State-Trait Anxiety Inventory, Parenting Stress Scale, Stress Response Inventory, and Brief Resilience Scale assessed mental health variable changes. Visual Analog Scales (VAS) were used to self-report neck, shoulders, back, and waist pain and assess stress, anxiety, relaxation, and confidence. We also measured pain, psychological VAS, and Heart Rate Variability (HRV) immediately before and after each yoga session.

RESULTS

The YG exhibited significant reductions in muscle pain, depression, stress response, fatigue, and frustration, whereas the CG expressed no change. Prop-assisted yoga immediately improved pain and psychological VAS. HRV analyses revealed instantly reduced heart rates and an R-R interval and standard deviation normal to normal (SDNN) increase.

CONCLUSIONS

Prop-assisted yoga may serve as a viable, safe, and efficient alternative therapeutic modality for managing chronic stress-related conditions.

Effects of Heart Rate Variability Biofeedback Training on Anxiety Reduction and Brain Activity: a Randomized Active-Controlled Study Using EEG

Heart rate variability biofeedback (HRVBF) is a promising anxiety-reducing intervention that increases vagally-mediated heart rate variability (vmHRV) through slow-paced breathing and feedback of heart rhythm. Several studies have reported the anxiety-reducing effects of HRVBF; however, some studies have reported such training as ineffective. Furthermore, the effects of training and underlying brain activity changes remain unclear. This study examined the anxiety-reducing effects of HRVBF training and related brain activity changes by randomly assigning participants, employing an active control group, and measuring anxiety-related attentional bias using the emotional Stroop task and electroencephalography (EEG). Fifty-five healthy students with anxiety were randomly assigned to the HRVBF or control groups, and 21 in the HRVBF group and 19 in the control group were included in the analysis. Both groups performed 10 training sessions of 20 min each within 3 weeks. They were assessed using resting vmHRV, event-related potential (ERP), time-frequency EEG, attentional bias, and the State-Trait Anxiety Inventory-JYZ (STAI-JYZ) before and after training. The results demonstrated increased resting vmHRV in the HRVBF group compared to the control group after training. However, no differences were observed in ERP, time-frequency EEG, attentional bias, and STAI-JYZ. Participants with higher pre-training resting vmHRV achieved higher heart rhythm coherence in HRVBF training and had reduced attentional bias. This study suggests that individuals with higher resting vmHRV are more likely to be proficient in HRVBF training and benefit from its anxiety-reducing effects. The findings contribute to participant selection to benefit from HRVBF training and modification of the training protocols for non-responders.Clinical trial registrationOrganization: University Hospital Medical Information Network Clinical Trials Registry (UMIN-CTR), JapanRegistration number: UMIN000047096Registration date: March 6, 2022.

Alleviating premenstrual symptoms with smartphone-based heart rate variability biofeedback training: a pilot study

Introduction

Heart rate variability biofeedback (HRVB) is a well-studied intervention known for its positive effects on emotional, cognitive, and physiological well-being, including relief from depressive symptoms. However, its practical use is hampered by high costs and a lack of trained professionals. Smartphone-based HRVB, which eliminates the need for external devices, offers a promising alternative, albeit with limited research. Additionally, premenstrual symptoms are highly prevalent among menstruating individuals, and there is a need for low-cost, accessible interventions with minimal side effects. With this pilot study, we aim to test, for the first time, the influence of smartphone-based HRVB on depressive and premenstrual symptoms, as well as anxiety/stress symptoms and attentional control.

Methods

Twenty-seven participants with above-average premenstrual or depressive symptoms underwent a 4-week photoplethysmography smartphone-based HRVB intervention using a waitlist-control design. Laboratory sessions were conducted before and after the intervention, spaced exactly 4 weeks apart. Assessments included resting vagally mediated heart rate variability (vmHRV), attentional control via the revised attention network test (ANT-R), depressive symptoms assessed with the BDI-II questionnaire, and stress/anxiety symptoms measured using the DASS questionnaire. Premenstrual symptomatology was recorded through the PAF questionnaire if applicable. Data analysis employed linear mixed models.

Results

We observed improvements in premenstrual, depressive, and anxiety/stress symptoms, as well as the Executive Functioning Score of the ANT-R during the intervention period but not during the waitlist phase. However, we did not find significant changes in vmHRV or the Orienting Score of the ANT-R.

Discussion

These findings are promising, both in terms of the effectiveness of smartphone-based HRVB and its potential to alleviate premenstrual symptoms. Nevertheless, to provide a solid recommendation regarding the use of HRVB for improving premenstrual symptoms, further research with a larger sample size is needed to replicate these effects.

The Utility of Heartrate and Heartrate Variability Biofeedback for the Improvement of Interoception across Behavioural, Physiological and Neural Outcome Measures: A Systematic Review

Interoceptive dysfunctions are increasingly implicated in a number of physical and mental health conditions. Accordingly, there is a pertinent need for therapeutic interventions which target interoceptive deficits. Heartrate and heartrate variability biofeedback therapy (HR(V)-BF), interventions which train individuals to regulate their cardiovascular signals and constrain these within optimal parameters through breathing, could enhance the functioning of interoceptive pathways via stimulation of the vagus nerve. Consequently, this narrative systematic review sought to synthesise the current state of the literature with regard to the potential of HR(V)-BF as an interoceptive intervention across behavioural, physiological and neural outcome measures related to interoception. In total, 77 papers were included in this review, with the majority using physiological outcome measures. Overall, findings were mixed with respect to improvements in the outcome measures after HR(V)-BF. However, trends suggested that effects on measures related to interoception were stronger when resonance frequency breathing and an intense treatment protocol were employed. Based on these findings, we propose a three-stage model by which HR(V)-BF may improve interoception which draws upon principles of interoceptive inference and predictive coding. Furthermore, we provide specific directions for future research, which will serve to advance the current knowledge state.

A Mendelian randomization study of the effect of mental disorders on cardiovascular disease

Objective

The effect of mental disorders (MD) on cardiovascular disease (CVD) remains controversial, and this study aims to analyze the causal relationship between eight MD and CVD by Mendelian randomization (MR).

Methods

Single nucleotide polymorphisms of attention-deficit/hyperactivity disorder (ADHD), anorexia nervosa (AN), anxiety disorder (ANX), autism spectrum disorder (ASD), bipolar disorder (BD), depression, obsessive-compulsive disorder (OCD), schizophrenia (SCZ), and CVD were obtained from UK Biobank and FinnGen. Exposure-outcome causality was tested using inverse variance weighted (IVW), MR-Egger, and weighted median. Horizontal pleiotropy and heterogeneity were assessed by MR-Egger intercept and Cochran's Q, respectively, while stability of results was assessed by leave-one-out sensitivity analysis.

Results

MR analysis showed that ANX (IVW [odds ratio (OR) 1.11, 95% confidence intervals (CI) 1.07-1.15, p < 0.001]; MR-Egger [OR 1.03, 95% CI 0.92-1.14, p = 0.652]; weighted median [OR 1.09, 95% CI 1.03-1.14, p = 0.001]), ASD (IVW [OR 1.05, 95% CI 1.00-1.09, p = 0.039]; MR-Egger [OR 0.95, 95% CI 0.84-1.07, p = 0.411]; weighted median [OR 1.01, 95% CI 0.96-1.06, p = 0.805]), depression (IVW [OR 1.15, 95% CI 1.10-1.19, p < 0.001]; MR-Egger [OR 1.10, 95% CI 0.96-1.26, p = 0.169]; weighted median [OR 1.13, 95% CI 1.08-1.19, p < 0.001]) were significantly associated with increased risk of CVD, whereas ADHD, AN, BD, OCD, and SCZ were not significantly associated with CVD (p > 0.05). Intercept analysis showed no horizontal pleiotropy (p > 0.05). Cochran's Q showed no heterogeneity except for BD (p = 0.035). Sensitivity analysis suggested that these results were robust.

Conclusions

ANX, ASD, and depression are associated with an increased risk of CVD, whereas AN, ADHD, BD, OCD, and SCZ are not causally associated with CVD. Active prevention and treatment of ANX, ASD, and depression may help reduce the risk of CVD.

Sympathovagal quotient and resting-state functional connectivity of control networks are related to gut Ruminococcaceae abundance in healthy men

INTRODUCTION

Heart rate variability (HRV), brain resting-state functional connectivity (rsFC), and gut microbiota (GM) are three recognized indicators of health status, whose relationship has not been characterized. We aimed to identify the GM genera and families related to HRV and rsFC, the interaction effect of HRV and rsFC on GM taxa abundance, and the mediation effect of diet on these relationships.

METHODS

Eighty-eight healthy, young Colombian men were included in this cross-sectional study. HRV metrics were extracted from 24-hour Holter monitoring data and the resting functional connectivity strength (FCS) of 15 networks were derived from functional magnetic resonance imaging. Gut microbiota composition was assessed using the sequences of the V3-V4 regions of the 16 S rRNA gene, and diet was evaluated using a food frequency questionnaire. Multivariate linear regression analyses were performed to evaluate the correlations between the independent variables (HRV metrics and FCS) and the dependent variables (GM taxa abundance or alpha diversity indexes). Mediation analyses were used to test the role of diet in the relationship between HRV and GM.

RESULTS

The sympathovagal quotient (SQ) and the FCS of control networks were positively correlated with the abundance of the gut Ruminococcaceae family and an unclassified Ruminococcaceae genus (Ruminococcaceae_unc). Additionally, the interaction between the FCS of the control network and SQ reduced the individual main effects on the Ruminococcaceae_unc abundance. Finally, reduced habitual fiber intake partially mediated the relationship between SQ and this genus.

CONCLUSION

Two indicators of self-regulation, HRV and the rsFC of control networks, are related to the abundance of gut microbiota taxa in healthy men. However, only HRV is related to habitual dietary intake; thus, HRV could serve as a marker of food choice and GM composition in the future.

Regulation of exercise on heart rate variability in perimenopausal and postmenopausal women

Heart rate variability (HRV) is a non-invasive quantitative measure of cardiac autonomic nervous activity. Due to the increase of age and the decrease of estrogen level in perimenopausal and postmenopausal women, the cardiac autonomic nervous function is abnormal, increasing the risk of cardiovascular disease. Proper exercise can increase estrogen levels, improve cardiovascular health, regulate cardiac autonomic nervous activity, and reduce the risk of cardiovascular disease. Low-moderate intensity aerobic exercise, resistance exercise, aerobic combined resistance exercise and mind-body exercise have positive effects on HRV in perimenopausal and postmenopausal women. Therefore, summarizing the effects of different exercise modes on HRV in perimenopausal and postmenopausal women, as well as the mechanism of exercise training improvement on HRV, so as to adopt better exercise strategies to improve HRV of perimenopausal and postmenopausal women, and thus reduce the risk of cardiovascular diseases and improve the health level and quality of life of perimenopausal and postmenopausal women.

Effects of cortisol administration on heart rate variability and functional connectivity across women with different depression histories

Abnormalities within the hypothalamic-pituitary-adrenal (HPA) axis and autonomic nervous system have been implicated in depression. Studies have reported glucocorticoid insensitivity and reduced heart rate variability (HRV) in depressive disorders. However, little is known about the effects of cortisol on HRV and resting-state functional connectivity (rsFC) of the central autonomic network (CAN) in depression. We collected resting-state fMRI and cardiac data for women with different depression histories (n = 61) after administration of cortisol and placebo using a double-blind crossover design. We computed rsFC for R-amygdala and L-amygdala seeds and assessed the change in HRV after cortisol (cortisol-placebo). Analyses examined the effects of acute cortisol administration on HRV and rsFC of the R-amygdala and L-amygdala. There was a significant interaction between HRV and treatment for rsFC between the amygdala and CAN regions. We found lower rsFC between the L-amygdala and putamen for those with a greater decrease in HRV after cortisol. There was also reduced rsFC between the R-amygdala and dorsomedial prefrontal cortex, putamen, middle cingulate cortex, insula, and cerebellum in those with lower HRV after cortisol. These results remained significant after adjusting for depression symptoms, age, and race. Our findings suggest that the effect of cortisol on CAN connectivity is related to its effects on HRV. Overall, these results could inform transdiagnostic interventions targeting HRV and the stress response systems across clinical and non-clinical populations.

Error-related cardiac deceleration: Functional interplay between error-related brain activity and autonomic nervous system in performance monitoring

Coordinated interactions between the central and autonomic nervous systems are crucial for survival due to the inherent propensity for human behavior to make errors. In our ever-changing environment, when individuals make mistakes, these errors can have life-threatening consequences. In response to errors, specific reactions occur in both brain activity and heart rate to detect and correct errors. Specifically, there are two brain-related indicators of error detection and awareness known as error-related negativity and error positivity. Conversely, error-related cardiac deceleration denotes a momentary slowing of heart rate following an error, signaling an autonomic response. However, what is the connection between the brain and the heart during error processing? In this review, we discuss the functional and neuroanatomical connections between the brain and heart markers of error processing, exploring the experimental conditions in which they covary. Given the current limitations of available data, future research will continue to investigate the neurobiological factors governing the brain-heart interaction, aiming to utilize them as combined markers for assessing cognitive control in healthy and pathological conditions.

Heart Rate Variability and Cognition: A Narrative Systematic Review of Longitudinal Studies

BACKGROUND

Heart rate variability (HRV) is a reliable and convenient method to assess autonomic function. Cross-sectional studies have established a link between HRV and cognition. Longitudinal studies are an emerging area of research with important clinical implications in terms of the predictive value of HRV for future cognition and in terms of the potential causal relationship between HRV and cognition. However, they have not yet been the objective of a systematic review. Therefore, the aim of this systematic review was to investigate the association between HRV and cognition in longitudinal studies.

METHODS

The review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The Embase, PsycINFO and PubMed databases were searched from the earliest available date to 26 June 2023. Studies were included if they involved adult human subjects and evaluated the longitudinal association between HRV and cognition. The risk of bias was assessed with the Newcastle-Ottawa Scale for Cohort Studies. The results were presented narratively.

RESULTS

Of 14,359 records screened, 12 studies were included in this systematic review, with a total of 24,390 participants. Two thirds of the studies were published from 2020 onwards. All studies found a longitudinal relationship between HRV and cognition. There was a consistent association between higher parasympathetic nervous system (PNS) activity and better cognition, and some association between higher sympathetic nervous system activity and worse cognition. Also, higher PNS activity persistently predicted better executive functioning, while data on episodic memory and language were more scant and/or controversial.

CONCLUSIONS

Our results support the role of HRV as a biomarker of future cognition and, potentially, as a therapeutic target to improve cognition. They will need confirmation by further, more comprehensive studies also including unequivocal non-HRV sympathetic measures and meta-analyses.

Heart Rate Variability Biofeedback in Adults with a Spinal Cord Injury: A Laboratory Framework and Case Series

Heart rate variability biofeedback (HRV-F) is a neurocardiac self-regulation therapy that aims to regulate cardiac autonomic nervous system activity and improve cardiac balance. Despite benefits in various clinical populations, no study has reported the effects of HRV-F in adults with a spinal cord injury (SCI). This article provides an overview of a neuropsychophysiological laboratory framework and reports the impact of an HRV-F training program on two adults with chronic SCI (T1 AIS A and T3 AIS C) with different degrees of remaining cardiac autonomic function. The HRV-F intervention involved 10 weeks of face-to-face and telehealth sessions with daily HRV-F home practice. Physiological (HRV, blood pressure variability (BPV), baroreflex sensitivity (BRS)), and self-reported assessments (Fatigue Severity Scale, Generalised Anxiety Disorder Scale, Patient Health Questionnaire, Appraisal of Disability and Participation Scale, EuroQol Visual Analogue Scale) were conducted at baseline and 10 weeks. Participants also completed weekly diaries capturing mood, anxiety, pain, sleep quality, fatigue, and adverse events. Results showed some improvement in HRV, BPV, and BRS. Additionally, participants self-reported some improvements in mood, fatigue, pain, quality of life, and self-perception. A 10-week HRV-F intervention was feasible in two participants with chronic SCI, warranting further investigation into its autonomic and psychosocial effects.

Cardiac Autonomic Balance Is Altered during the Acute Stress Response in Adolescent Major Depression-Effect of Sex

Autonomic nervous system (ANS) abnormalities are associated with major depressive disorder (MDD) already at adolescent age. The majority of studies so far evaluated parasympathetic and sympathetic branches of ANS individually, although composite indices including cardiac autonomic balance (CAB) and cardiac autonomic regulation (CAR) seem to measure ANS functioning more comprehensively and thus could provide better psychopathologies' predictors. We aimed to study CAB and CAR derived from high-frequency bands of heart rate variability and left ventricular ejection time during complex stress response (rest-Go/NoGo task-recovery) in MDD adolescents with respect to sex. We examined 85 MDD adolescents (52 girls, age: 15.7 ± 0.14 yrs.) and 80 age- and sex-matched controls. The MDD group showed significantly reduced CAB compared to controls at rest, in response to the Go/NoGo task, and in the recovery phase. Moreover, while depressed boys showed significantly lower CAB at rest and in response to the Go/NoGo task compared to control boys, depressed girls showed no significant differences in evaluated parameters compared to control girls. This study for the first time evaluated CAB and CAR indices in drug-naïve first-episode diagnosed MDD adolescents during complex stress responses, indicating an altered cardiac autonomic pattern (i.e., reciprocal sympathetic dominance associated with parasympathetic underactivity), which was predominant for depressed boys.

The effect of a single-session heart rate variability biofeedback on attentional control: does stress matter?

Introduction

Vagally mediated heart rate variability is an index of autonomic nervous system activity that is associated with a large variety of outcome variables including psychopathology and self-regulation. While practicing heart rate variability biofeedback over several weeks has been reliably associated with a number of positive outcomes, its acute effects are not well known. As the strongest association with vagally mediated heart rate variability has been found particularly within the attention-related subdomain of self-regulation, we investigated the acute effect of heart rate variability biofeedback on attentional control using the revised Attention Network Test.

Methods

Fifty-six participants were tested in two sessions. In one session each participant received a heart rate variability biofeedback intervention, and in the other session a control intervention of paced breathing at a normal ventilation rate. After the biofeedback or control intervention, participants completed the Attention Network Test using the Orienting Score as a measure of attentional control.

Results

Mixed models revealed that higher resting baseline vagally mediated heart rate variability was associated with better performance in attentional control, which suggests more efficient direction of attention to target stimuli. There was no significant main effect of the intervention on attentional control. However, an interaction effect indicated better performance in attentional control after biofeedback in individuals who reported higher current stress levels.

Discussion

The results point to acute beneficial effects of heart rate variability biofeedback on cognitive performance in highly stressed individuals. Although promising, the results need to be replicated in larger or more targeted samples in order to reach stronger conclusions about the effects.

Insular dysfunction of interoception in major depressive disorder: from the perspective of neuroimaging

Interoception plays a crucial role in maintaining bodily homeostasis and promoting survival, and is considered the basis of human emotion, cognition, and self-formation. A malfunction of interoception is increasingly suggested to be a fundamental component of different mental health conditions, and depressive disorders have been especially closely associated. Interoceptive signaling and processing depends on a system called the "interoceptive pathway," with the insula, located in the deep part of the lateral fissure, being the most important brain structure in this pathway. Neuroimaging studies have revealed alterations in the structure and function of the insula in a large number of individuals with depression, yet the precise relationship between these alterations and interoceptive dysfunction remains unclear. The goal of this review is to examine the evidence that exists for dysfunction of interoception in people with Major Depressive Disorder (MDD), and to determine the associated specific alterations in the structure and function of the insula revealed by neuroimaging. Overall, three aspects of the potential relationship between interoceptive dysfunction and alterations in insular function in people with depression have been assessed, namely clinical symptoms, quantitative measures of interoceptive function and ability, and interoceptive modulation. To conclude, several specific limitations of the published studies and important lines of enquiry for future research are offered.

A meta-analysis investigating the outcomes and correlation between heart rate variability biofeedback training on depressive symptoms and heart rate variability outcomes versus standard treatment in comorbid adult populations

BACKGROUND AND AIM

Heart rate variability biofeedback (HRVB) has previously been used to ameliorate depressive symptoms but its uses for tackling depressive symptoms in an array of comorbid adult patients is less established. This meta-analysis aims to evaluate whether HRVB is a useful tool to reduce depressive symptoms and improve HRV relative to standard treatment in adult comorbid populations, while also attempting to establish the association between the two outcomes.

METHODS

An extensive literature review was conducted using several databases including PubMed, Cinahl, Medline, Web of science and clinical.gov/UK register. A total of 149 studies were identified with 9 studies, totalling 428 participants were analysed using a random effects model.

RESULTS

Depressive outcomes yielded a mean effect size g=0.478 (CI 95% 0.212, 0.743) with HRV outcomes, yielding a mean effect size of g=0.223 (95% CI 0.036 to 0.411). Total heterogeneity was non-significant for depressive outcomes (Q= 13.77, p=0.088 I^=42.86%) and HRV (Q= 1.598, p=0.991, I^=0.000%) which indicates that little variance existed for the included studies.

CONCLUSIONS

In summary, the outcomes demonstrate that HRVB can improve both clinically relevant depressive symptoms and physiological HRV outcomes in various comorbid conditions in adult populations, while the correlation between the two was moderately negative, but non-significant.

At the heart of the matter: how mental stress and negative emotions affect atrial fibrillation

Atrial fibrillation (AF) is the most common form of cardiac arrhythmia, affecting 2%-3% of the world's population. Mental and emotional stress, as well as some mental health conditions (e.g., depression) have been shown to significantly impact the heart and have been suggested to act both as independent risk factors and triggers in the onset of AF. In this paper, we review the current literature to examine the role that mental and emotional stress have in the onset of AF and summarise the current knowledge on the interaction between the brain and heart, and the cortical and subcortical pathways involved in the response to stress. Review of the evidence suggests that mental and emotional stress negatively affect the cardiac system, potentially increasing the risk for developing and/or triggering AF. Further studies are required to further understand the cortical and sub-cortical structures involved in the mental stress response and how these interact with the cardiac system, which may help in defining new strategies and interventions to prevent the development of, and improve the management of AF.

The Utility of a Novel, Combined Biofeedback-Virtual Reality Device as Add-on Treatment for Chronic Migraine: A Randomized Pilot Study

OBJECTIVES

To determine if the frequent use of a combined biofeedback-virtual reality device improves headache-related outcomes in chronic migraine.

MATERIALS AND METHODS

In this randomized, controlled pilot study, 50 adults with chronic migraine were randomized to the experimental group (frequent use of a heart rate variability biofeedback-virtual reality device plus standard medical care; n=25) or wait-list control group (standard medical care alone; n=25). The primary outcome was a reduction in mean monthly headache days between groups at 12 weeks. Secondary outcomes included mean change in acute analgesic use frequency, depression, migraine-related disability, stress, insomnia, and catastrophizing between groups at 12 weeks. Tertiary outcomes included change in heart rate variability and device-related user experience measures.

RESULTS

A statistically significant reduction in mean monthly headache days between groups was not demonstrated at 12 weeks. However, statistically significant decreases in the mean frequency of total acute analgesic use per month (65% decrease in the experimental group versus 35% decrease in the control group, P <0.01) and depression score (35% decrease in the experimental group versus 0.5% increase in the control group; P <0.05) were shown at 12 weeks. At study completion, more than 50% of participants reported device satisfaction on a 5-level Likert scale.

DISCUSSION

Frequent use of a portable biofeedback-virtual reality device was associated with decreases in the frequency of acute analgesic use and in depression in individuals with chronic migraine. This platform holds promise as an add-on treatment for chronic migraine, especially for individuals aiming to decrease acute analgesic use or interested in nonmedication approaches.

Heart Rate Variability Covaries with Amygdala Functional Connectivity During Voluntary Emotion Regulation

The Neurovisceral Integration Model posits that shared neural networks support the effective regulation of emotions and heart rate, with heart rate variability (HRV) serving as an objective, peripheral index of prefrontal inhibitory control. Prior neuroimaging studies have predominantly examined both HRV and associated neural functional connectivity at rest, as opposed to contexts that require active emotion regulation. The present study sought to extend upon previous resting-state functional connectivity findings, examining task-related HRV and corresponding amygdala functional connectivity during a cognitive reappraisal task. Seventy adults (52 older and 18 younger adults, 18-84 years, 51% male) received instructions to cognitively reappraise negative affective images during functional MRI scanning. HRV measures were derived from a finger pulse signal throughout the scan. During the task, younger adults exhibited a significant inverse association between HRV and amygdala-medial prefrontal cortex (mPFC) functional connectivity, in which higher task-related HRV was correlated with weaker amygdala-mPFC coupling, whereas older adults displayed a slight positive, albeit non-significant correlation. Furthermore, voxelwise whole-brain functional connectivity analyses showed that higher task-based HRV was linked to weaker right amygdala-posterior cingulate cortex connectivity across older and younger adults, and in older adults, higher task-related HRV correlated positively with stronger right amygdala-right ventrolateral prefrontal cortex connectivity. Collectively, these findings highlight the importance of assessing HRV and neural functional connectivity during active regulatory contexts to further identify neural concomitants of HRV and adaptive emotion regulation.

Neuroimaging Studies of the Neural Correlates of Heart Rate Variability: A Systematic Review

Direct and indirect links between brain regions and cardiac function have been reported. We performed a systematic literature review to summarize current knowledge regarding the associations of heart rate variability (HRV) and brain region morphology, activity and connectivity involved in autonomic control at rest in healthy subjects. Both positive and negative correlations of cortical thickness and gray matter volumes of brain structures with HRV were observed. The strongest were found for a cluster located within the cingulate cortex. A decline in HRV, as well as cortical thickness with increasing age, especially in the orbitofrontal cortex were noted. When associations of region-specific brain activity with HRV were examined, HRV correlated most strongly with activity in the insula, cingulate cortex, frontal and prefrontal cortices, hippocampus, thalamus, striatum and amygdala. Furthermore, significant correlations, largely positive, between HRV and brain region connectivity (in the amygdala, cingulate cortex and prefrontal cortex) were observed. Notably, right-sided neural structures may be preferentially involved in heart rate and HRV control. However, the evidence for left hemispheric control of cardiac vagal function has also been reported. Our findings provide support for the premise that the brain and the heart are interconnected by both structural and functional networks and indicate complex multi-level interactions. Further studies of brain-heart associations promise to yield insights into their relationship to health and disease.

The effect of heart rate variability biofeedback in patients with acute coronary syndrome: A protocol for systematic review and meta-analysis

BACKGROUND

Acute coronary syndrome (ACS), the acute manifestation of ischemic heart disease, remains a major cause of morbidity and mortality worldwide. Soon after ACS, autonomic imbalance acts to preserve the proper functioning of the cardiovascular system and consequently of the whole body. In this study, we perform a protocol for systematic review and meta-analysis to evaluate the efficacy of heart rate variability biofeedback in improving the prognosis in patients with ACS.

METHODS

The protocol of this review was registered in PROSPERO (CRD42022379184). Meanwhile, it will be reported follow the guidelines of the preferred reporting items for systematic reviews and meta-analyses protocol. We will search 3 foreign electronic databases (Cochrane Library, Embase, Pubmed) and 4 Chinese electronic databases (China National Knowledge Infrastructure, WangFang Database, Chinese Biomedical Literature Database and Chinese Scientific Journal Database) to collect potential studies from their inceptions to December 2022. Risk of bias will be assessed according to the Cochrane Risk of Bias Tool. Data synthesis and statistical analysis will be performed using the RevMan 5.3 (The Nordic Cochrane Centre, The Cochrane Collaboration, Denmark) software.

RESULTS

The results of this systematic review will be published in a peer-reviewed journal.

CONCLUSION

This systematic review will provide high quality evidence to assess the efficacy of heart rate variability biofeedback in patients with ACS.

Squeeze the beat: Enhancing cardiac vagal activity during resonance breathing via coherent pelvic floor recruitment

Resonance breathing (RB) has been shown to benefit health and performance within clinical and non-clinical populations. This is attributed to its baroreflex stimulating effect and the concomitant increase in cardiac vagal activity (CVA). Hence, developing methods that strengthen the CVA boosting effect of RB could improve its clinical effectiveness. Therefore, we assessed whether supplementing RB with coherent pelvic floor activation (PRB), which has been shown to entrain the baroreflex, yields stronger CVA than standard RB. N = 32 participants performed 5-min of RB and PRB, which requires to recruit the pelvic floor during the complete inspiratory phase and release it at the initiation of the expiration. CVA was indexed via heart rate variability using RMSSD and LF-HRV. PRB induced significantly larger RMSSD (d = 1.04) and LF-HRV (d = 0.75, ps &lt; .001) as compared to RB. Results indicate that PRB induced an additional boost in CVA relative to RB in healthy individuals. However, subsequent studies are warranted to evaluate whether these first findings can be replicated in individuals with compromised health, including a more comprehensive psychophysiological assessment to potentially elucidate the origin of the observed effects. Importantly, longitudinal studies need to address whether PRB translates to better treatment outcomes.

Breathing out dental fear: A feasibility crossover study on the effectiveness of diaphragmatic breathing in children sitting on the dentist's chair

BACKGROUND

Anxiety related to the dental context is a clinically significant challenge. In children, dental fear is often accompanied by disruptive and uncooperative behaviours that can render treatment difficult. Although techniques to reduce children's anxiety exist, many have not been formally evaluated.

DESIGN

Diaphragmatic breathing has been shown to reduce fear and anxiety, but few investigations have evaluated whether it can reduce dental anxiety in children. This crossover study tested the effectiveness and feasibility of diaphragmatic breathing in twenty children undergoing dental care.

RESULTS

Compared with the treatment as usual, such a simple technique had significant benefits on mood, self-reported pain and autonomic balance, thus reducing sympathetic activation.

CONCLUSION

Diaphragmatic breathing is a low-cost, easy-to-implement technique suitable for daily dental practice, and is a promising tool for reducing negative effect and physiological distress in children with dental anxiety that results in more cooperative behaviours and reduced visit time.

The Effect of Heart Rate Variability Biofeedback Training on Vagal Tone in Athletically Talented Secondary School Students

This study examines whether twelve sessions of heart rate variability biofeedback training would improve vagally mediated heart rate variability. If so, it would go some way in explaining why breathing-based interventions reduce clinical symptoms and improve non-clinical performance outcomes. Methods: Thirty participants (N = 30, Nfemale = 13) aged 14–13-year-old, all talented athletes, from a sport specialist school in SE London UK, were randomly divided into three groups, a control group, a psychology skills training combined with heart rate variability biofeedback training group, and a heart rate variability biofeedback only group. For the combined group, a variety of typical psychological skill training techniques were also used. Results: Paired participant t-test and the Wilcoxon Signed Rank test found non-significant differences between pre- and post-intervention measurements of heart rate variability. Non-significant results remained even after pooling the biofeedback training groups (n = 19). Conclusions: Our results do not indicate that beneficial effects associated with focused breathing training can be attributed to improved vagal tone. Further investigation into the underlying mechanisms of the benefits of focused breathing techniques is necessary to maximize clinical and non-clinical outcomes.

Respiratory sinus arrhythmia during biofeedback is linked to persistent improvements in attention, short-term memory, and positive self-referential episodic memory

Background

Heart rate variability (HRV) biofeedback, an intervention based on the voluntary self-regulation of autonomic parameters, has been shown to affect prefrontal brain functioning and improve executive functions. The interest in using HRV biofeedback as cognitive training is typically ascribed to parasympathetic activation and optimized physiological functioning deriving from increased cardiac vagal control. However, the persistence of cognitive effects is poorly studied and their association with biofeedback-evoked autonomic changes has not yet been explored. In addition, no study has so far investigated the influence of HRV biofeedback in adults on long-term episodic memory, which is particularly concerned with self-referential encoding processing.

Methods

In the present study, a novel training system was developed integrating HRV and respiratory biofeedback into an immersive virtual reality environment to enhance training efficacy. Twenty-two young healthy adults were subjected to a blinded randomized placebo-controlled experiment, including six self-regulation training sessions, to evaluate the effect of biofeedback on autonomic and cognitive changes. Cardiac vagal control was assessed before, during, and 5 min after each training session. Executive functions, episodic memory, and the self-referential encoding effect were evaluated 1 week before and after the training program using a set of validated tasks.

Results

Linear mixed-effects models showed that HRV biofeedback greatly stimulated respiratory sinus arrhythmia during and after training. Moreover, it improved the attentional capabilities required for the identification and discrimination of stimuli ( η p 2 = 0.17), auditory short-term memory ( η p 2 = 0.23), and self-referential episodic memory recollection of positive stimuli ( η p 2 = 0.23). Episodic memory outcomes indicated that HRV biofeedback reinforced positive self-reference encoding processing. Cognitive changes were strongly dependent on the level of respiratory sinus arrhythmia evoked during self-regulation training.

Conclusion

The present study provides evidence that biofeedback moderates respiration-related cardiac vagal control, which in turn mediates improvements in several cognitive processes crucial for everyday functioning including episodic memory, that are maintained beyond the training period. The results highlight the interest in HRV biofeedback as an innovative research tool and medication-free therapeutic approach to affect autonomic and neurocognitive functioning. Finally, a neurocognitive model of biofeedback-supported autonomic self-regulation as a scaffolding for episodic memory is proposed.

Depressive rumination and heart rate variability: A pilot study on the effect of biofeedback on rumination and its physiological concomitants

Objective

Recent studies suggest that lower resting heart rate variability (HRV) is associated with elevated vulnerability to depressive rumination. In this study, we tested whether increases in HRV after HRV-biofeedback training are accompanied by reductions in rumination levels.

Materials and methods

Sixteen patients suffering from depression completed a 6-week HRV-biofeedback training and fourteen patients completed a control condition in which there was no intervention (waitlist). The training included five sessions per week at home using a smartphone application and an ECG belt. Depressive symptoms and autonomic function at rest and during induced rumination were assessed before and after each of the two conditions. We used a well-established rumination induction task to provoke a state of pervasive rumination while recording various physiological signals simultaneously. Changes in HRV, respiration rate, skin conductance, and pupil diameter were compared between conditions and time points.

Results

A significant correlation was found between resting HRV and rumination levels, both assessed at the first laboratory session (r = -0.43, p < 0.05). Induction of rumination led to an acceleration of heart rate and skin conductance increases. After biofeedback training, resting vagal HRV was increased (p < 0.01) and self-ratings of state anxiety (p < 0.05), rumination (p < 0.05), perceived stress (p < 0.05), and depressive symptoms (QIDS, BDI; both p < 0.05) were decreased. In the control condition, there were no changes in autonomic indices or depressive symptomatology. A significant interaction effect group x time on HRV was observed.

Conclusion

Our results indicate that a smartphone-based HRV-biofeedback intervention can be applied to improve cardiovagal function and to reduce depressive symptoms including self-rated rumination tendencies.

Enhancing Brain Connectivity With Infra-Low Frequency Neurofeedback During Aging: A Pilot Study

Aging is associated with decreased functional connectivity in the main brain networks, which can underlie changes in cognitive and emotional processing. Neurofeedback is a promising non-pharmacological approach for the enhancement of brain connectivity. Previously, we showed that a single session of infra-low frequency neurofeedback results in increased connectivity between sensory processing networks in healthy young adults. In the current pilot study, we aimed to evaluate the possibility of enhancing brain connectivity during aging with the use of infra-low frequency neurofeedback. Nine females aged 52 ± 7 years with subclinical signs of emotional dysregulation, including anxiety, mild depression, and somatoform symptoms, underwent 15 sessions of training. A resting-state functional MRI scan was acquired before and after the training. A hypothesis-free intrinsic connectivity analysis showed increased connectivity in regions in the bilateral temporal fusiform cortex, right supplementary motor area, left amygdala, left temporal pole, and cerebellum. Next, a seed-to-voxel analysis for the revealed regions was performed using the post- vs. pre-neurofeedback contrast. Finally, to explore the whole network of neurofeedback-related connectivity changes, the regions revealed by the intrinsic connectivity and seed-to-voxel analyses were entered into a network-based statistical analysis. An extended network was revealed, including the temporal and occipital fusiform cortex, multiple areas from the visual cortex, the right posterior superior temporal sulcus, the amygdala, the temporal poles, the superior parietal lobule, and the supplementary motor cortex. Clinically, decreases in alexithymia, depression, and anxiety levels were observed. Thus, infra-low frequency neurofeedback appears to be a promising method for enhancing brain connectivity during aging, and subsequent sham-controlled studies utilizing larger samples are feasible.

My Life in HRV Biofeedback Research

This paper reviews the published work of me along with my students and close colleagues on the topic of heart rate variability biofeedback (HRVB). It includes early research by Vaschillo documenting resonance characteristics of the baroreflex system that causes large oscillations in heart rate when breathing at resonance frequency, research on heart rate variability as a marker of parasympathetic stress response in asthma, and HRVB as a treatment for asthma and depression. Many questions about HRVB remain unresolved, and important questions for future research are listed.

Meditation and Aerobic Exercise Enhance Mental Health Outcomes and Pattern Separation Learning Without Changing Heart Rate Variability in Women with HIV

Mental and physical (MAP) training targets the brain and the body through a combination of focused-attention meditation and aerobic exercise. The following feasibility pilot study tested whether 6 weeks of MAP training improves mental health outcomes, while enhancing discrimination learning and heart rate variability (HRV) in a group of women living with human immunodeficiency virus (HIV) and other stress-related conditions. Participants were assigned to training (n = 18) or no-training control (n = 8) groups depending on their ability and willingness to participate, and if their schedule allowed. Training sessions were held once a week for 6 weeks with 30 min of meditation followed by 30 min of aerobic exercise. Before and after 6 weeks of training, participants completed the Behavioral Pattern Separation Task as a measure of discrimination learning, self-report questionnaires of ruminative and trauma-related thoughts, depression, anxiety, and perceived stress, and an assessment of HRV at rest. After training, participants reported fewer ruminative and trauma-related thoughts, fewer depressive and anxiety symptoms, and less perceived stress (p's < 0.05). The positive impact on ruminative thoughts and depressive symptoms persisted 6 months after training. They also demonstrated enhanced discrimination of similar patterns of information (p < 0.05). HRV did not change after training (p > 0.05). Combining mental and physical training is an effective program for enhancing mental health and aspects of cognition in women living with HIV, although not necessarily through variance in heart rate.

Measuring Heart Rate Variability in Patients Admitted with ST-Elevation Myocardial Infarction for the Prediction of Subsequent Cardiovascular Events: A Systematic Review

Background and objectives: Ischemic heart disease represents the leading cause of death, emphasizing risk stratification and early therapeutic intervention. Heart rate variability (HRV), an indirect marker of autonomic nervous system activity, was investigated extensively as a risk factor for adverse cardiovascular events following acute myocardial infarction. Thus, we systematically reviewed the literature to investigate the association of HRV parameters with mortality and adverse cardiovascular events in patients presenting with ST-elevation myocardial infarction (STEMI). Materials and methods: Following the search process in the MEDLINE (PubMed), Embase, and Cochrane databases, nine studies were included in the final analysis. Results: Lower time-domain HRV parameters and a higher ratio between power in the low-frequency (LF) band and power in the high-frequency (HF) band (LF/HF) were associated with higher all-cause mortality during follow-up, even in patients treated mainly with percutaneous coronary interventions (PCI). Although most studies measured HRV on 24 h ECG recordings, short- and ultra-short-term measures (1 min and 10 s, respectively) were also associated with an increased risk of all-cause mortality. Although data were discrepant, some studies found an association between HRV and cardiac mortality, reinfarction, and other major adverse cardiovascular events. Conclusions: In conclusion, HRV measurement in patients with STEMI could bring crucial prognostic information, as it was associated with an increased risk of all-cause mortality documented in clinical studies. More and larger clinical trials are required to validate these findings in contemporary patients with STEMI in the context of the new generation of drug-eluting stents and current antithrombotic and risk-modifying therapies.