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

Kozasa Y., Nakashima N., Ito M., Ishikawa T., Kimoto H., Ushijima K., Makita N., Takano M.

The contribution of HCN4 pacemaker channels in the autonomic regulation of the sino-atrial node (SAN) has been a matter of debate. The transgenic overexpression of HCN4 did not induce tachycardia, but reduced heart rate variability, while the conditional knockdown of HCN4 gave rise to sinus arrhythmia. The response of the SAN to β-adrenergic stimulation was not affected by overexpression or knockdown of HCN4 channels. When HCN4 channels were knocked down, the parasympathetic response examined by cervical vagus nerve stimulation (CVNS) was enhanced; the CVNS induced complete sinus pause. The overexpression of HCN4 attenuated bradycardia induced by CVNS only during β-adrenergic stimulation. We concluded that HCN4 pacemaker channels stabilize the spontaneous firing by attenuating the parasympathetic response of the SAN.The heart rate is dynamically controlled by the sympathetic and parasympathetic nervous systems that regulate the sinoatrial node (SAN). HCN4 pacemaker channels are the well-known causative molecule of congenital sick sinus syndrome. Although HCN4 channels are activated by cAMP, the sympathetic response of the SAN was preserved in patients carrying loss-of-function mutations of the HCN4 gene. In order to clarify the contribution of HCN4 channels in the autonomic regulation of the SAN, we developed novel gain-of-function mutant mice in which the expression level of HCN4 channels could be reversibly changed from zero to ∼3 times that in wild-type mice, using tetracycline transactivator and the tetracycline responsive element. We recorded telemetric ECGs in freely moving conscious mice and analysed the heart rate variability. We also evaluated the response of the SAN to cervical vagus nerve stimulation (CVNS). The conditional overexpression of HCN4 did not induce tachycardia, but reduced heart rate variability. The HCN4 overexpression also attenuated bradycardia induced by the CVNS only during the β-adrenergic stimulation. In contrast, the knockdown of HCN4 gave rise to sinus arrhythmia, and enhanced the parasympathetic response; complete sinus pause was induced by the CVNS. In vitro, we compared the effects of acetylcholine on the spontaneous action potentials of single pacemaker cells, and found that similar phenotypic changes were induced by genetic manipulation of HCN4 expression both in the presence and absence of β-adrenergic stimulation. Our study suggests that HCN4 channels attenuate the vagal response of the SAN, and thereby stabilize the spontaneous firing of the SAN.

Boyett M.R., Wang Y., Nakao S., Ariyaratnam J., Hart G., Monfredi O., D’Souza A.

Boyett M.R.

van Roon A.M., Snieder H., Lefrandt J.D., de Geus E.J., Riese H.

In their article, Monfredi et al1 addressed the relationship between mean heart rate (HR) and its variability (HRV). In their carefully conducted experiments and with clear reasoning, they demonstrated a universal exponential decay-like relationship between HRV and HR and concluded from this that HRV cannot be used in any simple way to assess autonomic nerve activity to the heart. Like Stauss,2 we tend to agree with this conclusion as it points out a highly relevant and important issue in the field of cardiovascular medicine. However, we note that the complex biophysical model presented is merely an example of a restriction-of-range phenomena, which has been acknowledged in psychophysiological research3,4. These insights were not picked-up and included in the guiding HRV Task Force paper5 and likely, therefore, largely missed. Thirty years ago, Akselrod et al6 elegantly explained that the nature of the interbeat interval (IBI) time series can explain the relationship between HRV and HR. In …

Sloan R.P., Schwarz E., McKinley P.S., Weinstein M., Love G., Ryff C., Mroczek D., Choo T., Lee S., Seeman T.

High frequency (HF) heart rate variability (HRV) has long been accepted as an index of cardiac vagal control. Recent studies report relationships between HF-HRV and indices of positive and negative affect, personality traits and well-being but these studies generally are based on small and selective samples.These relationships were examined using data from 967 participants in the second Midlife in the U.S. (MIDUS II) study. Participants completed survey questionnaires on well-being and affect. HF-HRV was measured at rest. A hierarchical series of regression analyses examined relationships between these various indices and HF-HRV before and after adjustment for relevant demographic and biomedical factors.Significant inverse relationships were found only between indices of negative affect and HF-HRV. Relationships between indices of psychological and hedonic well-being and positive affect failed to reach significance.These findings raise questions about relationships between cardiac parasympathetic modulation, emotion regulation, and indices of well-being. (PsycINFO Database Record

Beauchaine T.P., Thayer J.F.

The Research Domain Criteria (RDoC), developed by the National Institute of Mental Health as a neuroscience-informed alternative to traditional psychiatric nosology, is an explicitly dimensional system in which classification of psychopathology is derived inductively (i.e., from basic science), across multiple levels of analysis (e.g., genetic, neural, psychophysiological, and behavioral). Although RDoC is often presented as paradigmatically revolutionary, a review of the history of psychophysiology suggests that roots of RDoC thinking extend at least as far back as the mid-20th Century. In this paper, we briefly and selectively review the historical emergence of neurobiologically-informed dimensional trait models of psychopathology, and we summarize our thinking regarding high frequency heart rate variability (HF-HRV) as a transdiagnostic biomarker of self-regulation and cognitive control. When functional interactions between HF-HRV and systems of behavioral approach and avoidance are considered, diverse patterns of behavioral maladjustment can be subsumed into a single model. This model accommodates the general bifactor structure of psychopathology, and suggests that HF-HRV can be viewed as an autonomic, transdiagnostic biomarker of mental illness.

Neijts M., van Lien R., Kupper N., Boomsma D., Willemsen G., de Geus E.J.

Measurements of ambulatory autonomic reactivity can help with our understanding of the long-term health consequences of exposure to psychosocial stress in real-life settings.In this study, unstructured 24-hour ambulatory recordings of cardiac parasympathetic and sympathetic control were obtained in 1288 twins and siblings, spanning both work time and leisure time. These data were used to define two ambulatory baseline (sleep, leisure) and four stress conditions (wake, work, work_sitting, work_peak) from which six ambulatory stress reactivity measures were derived. The use of twin families allowed for estimation of heritability and testing for the amplification of existing or emergence of new genetic variance during stress compared with baseline conditions.Temporal stability of ambulatory reactivity was assessed in 62 participants and was moderate to high over a 3-year period (0.36 < r < 0.91). Depending on the definition of ambulatory reactivity used, significant heritability was found, ranging from 29% to 40% for heart rate, 34% to 47% for cardiac parasympathetic control (indexed as respiratory sinus arrhythmia), and 10% to 19% for cardiac sympathetic control (indexed as the preejection period). Heritability of ambulatory reactivity was largely due to newly emerging genetic variance during stress compared with periods of rest. Interestingly, reactivity to short standardized stressors was poorly correlated with the ambulatory reactivity measures implying poor laboratory-real-life correspondence.Ambulatory autonomic reactivity extracted from an unstructured real-life setting shows reliable, stable, and heritable individual differences. Real-life situations uncover a new and different genetic variation compared with that seen in resting baseline conditions, including sleep.

Bartos D.C., Grandi E., Ripplinger C.M.

Optimal cardiac function depends on proper timing of excitation and contraction in various regions of the heart, as well as on appropriate heart rate. This is accomplished via specialized electrical properties of various components of the system, including the sinoatrial node, atria, atrioventricular node, His-Purkinje system, and ventricles. Here we review the major regionally determined electrical properties of these cardiac regions and present the available data regarding the molecular and ionic bases of regional cardiac function and dysfunction. Understanding these differences is of fundamental importance for the investigation of arrhythmia mechanisms and pharmacotherapy. © 2015 American Physiological Society. Compr Physiol 5:1423-1464, 2015.

Dias da Silva V.J., Tobaldini E., Rocchetti M., Wu M.A., Malfatto G., Montano N., Zaza A.

Bradycardic agents are currently used in the treatment of angina and heart failure; direct information on their effects on cardiac sympathetic nerve activity (SNA) may be relevant to their chronic use. The present study evaluates the effect of pacemaker inhibition on SNA; direct nerve recordings and indirect autonomic indexes are compared.Experiments were performed in 18 anaesthetized rats. SNA (direct nerve recording) and heart rate variability (HRV) indexes were evaluated in parallel. All parameters were recorded 10 min before to 60 min after administration of the If blocker ivabradine (IVA; 2 mg/kg, i.v.; n = 8) or vehicle (VEH; n = 5). IVA-induced RR interval (RR) prolongation (at 60 min +15.0 ± 7.1%, P < 0.01) was associated with decreased diastolic arterial pressure (DAP; -17.3 ± 8.4%, P < 0.05) and increased SNA (+51.1 ± 12.3%, P < 0.05). These effects were accompanied by increased RR variance (RRσ(2)), which showed strong positive correlation with RR. Frequency-domain HRV indexes (in normalized units) were unchanged by IVA. After baroreceptor reflexes had been eliminated by sino-aortic denervation (n = 5), similar IVA-induced RR prolongation (at 60 min +14.3 ± 5.9%, NS vs. intact) was associated with a larger DAP reduction (-30.9 ± 4.1%, P < 0.05 vs. intact), but failed to affect SNA.(i) IVA-induced bradycardia was associated with increased SNA, resulting from baroreceptor unloading; if this applied to chronic IVA use in humans, it would be of relevance for therapeutic use of the drug. (ii) Whenever mean HR is concomitantly changed, time-domain HRV indexes should not be unequivocally interpreted in terms of autonomic balance.

Monfredi O., Zhang H., Boyett M.R.

Circulation recently published the work of Soares-Miranda et al,1 in which physical activity and heart rate variability (HRV) in older adults were evaluated. The authors showed that greater leisure activity, walking distance, and walking pace are associated with higher HRV, which they interpreted as better autonomic function. We have reservations concerning this conclusion. First, physical activity lowers resting heart rate (HR).2 It is established that time- and frequency-domain measures of HRV are nonlinearly dependent on HR, with low HRV being intrinsically linked to a higher HR, and vice versa.3–5 We argue that HRV is a nonlinear surrogate of HR.3 Soares-Miranda et …

Stauss H.M.

See related article, pp 1334–1343 In this issue of Hypertension , Monfredi et al1 address a phenomenon that has been repeatedly described in the literature2–5 but, nevertheless, went largely unnoticed by the scientific community using heart rate variability (HRV) to assess cardiac autonomic control or to predict cardiovascular health. The phenomenon studied by Monfredi et al1 is that most HRV parameters are inversely related to the actual level of HR, such that HRV is usually lower if HR is high and vice versa. The importance of the work by Monfredi et al1 is that it explores the physiological mechanisms underlying the relationship between HR and HRV using mathematical and biophysical models applied to data from various species and even in vitro preparations with differing levels of mean HR. Furthermore, using the standard deviation (SD) of normal to normal intervals6 as an example of one of the more frequently used HRV parameters; they provide a simple equation that can be used to normalize this HRV parameter so that it is independent of the actual level of HR. By convention, HRV is typically calculated from RR-interval and not from HR time series.6 As pointed out in a recent review article by Sacha,4 the relationship between HRV (calculated from RR-intervals) and HR is partly because of the inverse relationship between HR and RR-interval (eg, if HR fluctuates by ±10 bpm, the corresponding fluctuations in RR-intervals are ±250 ms at an average HR of 50 bpm but only ±60 ms at an average HR of 100 bpm). Thus, if HRV is calculated from RR-intervals, a …

Monfredi O., Lyashkov A.E., Johnsen A., Inada S., Schneider H., Wang R., Nirmalan M., Wisloff U., Maltsev V.A., Lakatta E.G., Zhang H., Boyett M.R.

Heart rate (HR) variability (HRV; beat-to-beat changes in the R-wave to R-wave interval) has attracted considerable attention during the past 30+ years (PubMed currently lists >17 000 publications). Clinically, a decrease in HRV is correlated to higher morbidity and mortality in diverse conditions, from heart disease to fetal distress. It is usually attributed to fluctuation in cardiac autonomic nerve activity. We calculated HRV parameters from a variety of cardiac preparations (including humans, living animals, Langendorff-perfused heart, and single sinoatrial nodal cell) in diverse species, combining this with data from previously published articles. We show that regardless of conditions, there is a universal exponential decay-like relationship between HRV and HR. Using 2 biophysical models, we develop a theory for this and confirm that HRV is primarily dependent on HR and cannot be used in any simple way to assess autonomic nerve activity to the heart. We suggest that the correlation between a change in HRV and altered morbidity and mortality is substantially attributable to the concurrent change in HR. This calls for re-evaluation of the findings from many articles that have not adjusted properly or at all for HR differences when comparing HRV in multiple circumstances.

Huikuri H.V., Stein P.K.

Heart rate (HR) variability has been extensively studied in cardiac patients, especially in patients surviving an acute myocardial infarction (AMI) and also in patients with congestive heart failure (CHF) or left ventricular (LV) dysfunction. The majority of studies have shown that patients with reduced or abnormal HR variability have an increased risk of mortality within a few years after an AMI or after a diagnosis of CHF/LV dysfunction. Various measures of HR dynamics, such as time-domain, spectral, and non-linear measures of HR variability have been used in risk stratification. The prognostic power of various measures, except of those reflecting rapid R-R interval oscillations, has been almost identical, albeit some non-linear HR variability measures, such as short-term fractal scaling exponent have provided somewhat better prognostic information than the others. Abnormal HR variability predicts both sudden and non-sudden cardiac death. Because of remodeling of the arrhythmia substrate after AMI, early measurement of HR variability to identify those at high risk should likely be repeated later in order to assess the risk of fatal arrhythmia events. Future randomized trials using HR variability/turbulence as one of the pre-defined inclusion criteria will show whether routine measurement of HR variability/turbulence will become a routine clinical tool for risk stratification of cardiac patients.

Sacha J., Barabach S., Statkiewicz-Barabach G., Sacha K., Müller A., Piskorski J., Barthel P., Schmidt G.

Graziano P., Derefinko K.

Polyvagal theory has influenced research on the role of cardiac vagal control, indexed by respiratory sinus arrhythmia withdrawal (RSA-W) during challenging states, in children's self-regulation. However, it remains unclear how well RSA-W predicts adaptive functioning (AF) outcomes and whether certain caveats of measuring RSA (e.g., respiration) significantly impact these associations. A meta-analysis of 44 studies (n=4996 children) revealed small effect sizes such that greater levels of RSA-W were related to fewer externalizing, internalizing, and cognitive/academic problems. In contrast, RSA-W was differentially related to children's social problems according to sample type (community vs. clinical/at-risk). The relations between RSA-W and children's AF outcomes were stronger among studies that co-varied baseline RSA and in Caucasian children (no effect was found for respiration). Children from clinical/at-risk samples displayed lower levels of baseline RSA and RSA-W compared to children from community samples. Theoretical/practical implications for the study of cardiac vagal control are discussed.

Zhang R., Hong J., Zheng X., Chen S., Lin L., Xiao Y.

ObjectivesChanges in poststroke heart rate variability (HRV) might be helpful for early identification of patients with neurological impairment and poor prognosis, which could allow for early intervention to reduce adverse outcomes. The aim of this study is to perform a scoping review to identify the influence of poststroke HRV on the neurological impairment severity and the prognosis among patients with ischaemic stroke (IS).DesignThe study design allows us to examine existing research, identify the research gaps and target the important areas for future research. In the search and report process, the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews guidelines and checklist were used.Data sourcesThree databases (PubMed, Web of Science and Ovid MEDLINE (Ovid)) were searched before December 2023.Eligibility criteria for selecting studiesThe literature related to the topic of this study was mainly included, and the articles were excluded if they only focused on cerebral haemorrhage or were reviews, guidelines, books, etc.Data extraction and synthesisDescriptive analysis was used to display the distribution of the included studies and then the summary method was adopted for further analysing.Results3251 articles that may be related to the scoping review topic were screened. After title and abstract screening and full-text reading, 21 records were finally included. Whether at discharge (n=6) or after follow-up (n=11), it was found that when the SD of all normal-to-normal intervals (SDNN) or the SD of the averages of normal-to-normal intervals decreased, the neurological impairment severity would be increased, including dysarthria, aphasia and hemiplegia. The root mean square of successive differences, the ratio of low frequency to high frequency and the high frequency were valuable predictors for the occurrence of adverse cardiocerebrovascular events. And the poor prognosis among patients with IS might be influenced by SDNN.ConclusionThis scoping review confirmed that post-IS HRV indicators can predict neurological impairment and prognosis of patients with stroke, highlighting a potential direction for early intervention. Large independent cohorts should be used to evaluate the predictive performance, reliability and potential limitations of these indicators in the future, and it will be important to explore interventions that make HRV change.

Hager T., Agorastos A., Ögren S.O., Stiedl O.

Background: The beat-by-beat fluctuation of heart rate (HR) in its temporal sequence (HR dynamics) provides information on HR regulation by the autonomic nervous system (ANS) and its dysregulation in pathological states. Commonly, linear analyses of HR and its variability (HRV) are used to draw conclusions about pathological states despite clear statistical and translational limitations. Objective: The main aim of this study was to compare linear and nonlinear HR measures, including detrended fluctuation analysis (DFA), based on ECG recordings by radiotelemetry in C57BL/6N mice to identify pathological HR dynamics. Methods: We investigated different behavioral and a wide range of pharmacological interventions which alter ANS regulation through various peripheral and/or central mechanisms including receptors implicated in psychiatric disorders. This spectrum of interventions served as a reference system for comparison of linear and nonlinear HR measures to identify pathological states. Results: Physiological HR dynamics constitute a self-similar, scale-invariant, fractal process with persistent intrinsic long-range correlations resulting in physiological DFA scaling coefficients of α~1. Strongly altered DFA scaling coefficients (α ≠ 1) indicate pathological states of HR dynamics as elicited by (1) parasympathetic blockade, (2) parasympathetic overactivation and (3) sympathetic overactivation but not inhibition. The DFA scaling coefficients are identical in mice and humans under physiological conditions with identical pathological states by defined pharmacological interventions. Conclusions: Here, we show the importance of tonic vagal function for physiological HR dynamics in mice, as reported in humans. Unlike linear measures, DFA provides an important translational measure that reliably identifies pathological HR dynamics based on altered ANS control by pharmacological interventions. Central ANS dysregulation represents a likely mechanism of increased cardiac mortality in psychiatric disorders.

Atanackov P., Peterlin J., Derlink M., Kovačič U., Kejžar N., Bajrović F.F.

Background/Objective: Heart rate variability (HRV) is a key biomarker of autonomic function, linked to morbidity and mortality across various diseases. Transcutaneous auricular vagus nerve stimulation (taVNS) shows therapeutic promise, but its effects on HRV and the influence of specific stimulation parameters remain unclear. This study investigated whether the acute effects of taVNS on HRV depend on combinations of stimulation frequency and pulse width. Methods: Seventy-eight healthy adults participated in seven randomized sessions, each testing one of six active taVNS protocols or an inactive sham condition applied to the cymba conchae of the left ear. The active protocols varied by frequency (10 Hz or 25 Hz) and pulse width (100 µs, 250 µs, or 500 µs). The sessions included 15 min of baseline, 15 min of taVNS or sham condition, and 10 min of recovery. HRV was calculated using the standard deviation of NN intervals (SDNN) and the root mean square of successive differences (RMSSD) from continuous ECG recordings. Results: The 10 Hz/250 µs, 10 Hz/500 µs, and 25 Hz/100 µs protocols significantly increased SDNN time series compared to the sham condition. Exploratory analysis revealed SDNN increases during the second 5 min of stimulation with the 10 Hz/500 µs protocol and during the first 5 min of recovery with the 10 Hz/250 µs and 25 Hz/100 µs protocols. No significant changes in the RMSSD were found for any protocol. Conclusions: TaVNS is safe in healthy adults, and specific frequency and pulse width combinations can acutely enhance overall HRV, as reflected in SDNN, but do not affect vagally mediated HRV, as reflected by the RMSSD. Future studies should optimize taVNS parameters to maximize physiological and clinical outcomes.

Shvartz V., Danilov V., Koroleva S., Shvartz E., Donakanyan S., Permyakov V., Erastova N., Golukhova E., Radikovna B.A., Viktorovich K.V., Andreevna F.A., Vitalievich M.V., Kazbekovna P.Z., Nikolaevich S.V., Andreevich Y.A., et. al.

To obtain reference ranges for heart rate variability (HRV) parameters in healthy children, taking into account their gender and age. The study included the results of testing 22,468 children ranging 5.5–12.5 years of age. The data were grouped by age and gender. The analysis of HRV parameters was carried out according to the standards described in existing guidelines. It was based on a 5-min rhythmogram obtained from a standard 12-lead electrocardiogram (ECG). The following characteristics of the temporal and spectral analyses of HRV were studied: standard deviation of NN intervals (SDNN), power in the low-frequency band of the HRV spectrum (LF), low-frequency power as mean percentage of total power (TP) of HRV spectrum (LF%), power in the high-frequency band of the HRV spectrum (HF), high-frequency power as mean percentage of TP of HRV spectrum (HF%), power in the very-low-frequency band of HRV (VLF), and LF/HF ratio. The values of SDNN, LF, HF, HF% and TP increased with age, reaching a peak at 8 and 9 years of age. It is notable that the values of SDNN, LF and TP were significantly lower in girls in each age group. The values of LF% and LF/HF decreased with age, with a peak decrease at 8 and 9 years of age, followed by a moderate increase or stabilization. The values of LF% and LF/HF did not differ statistically significantly between boys and girls. The VLF parameter exhibited a clear trend of growth with age and had higher values in boys of each age group. The correlation between HRV and heart rate (HR) was statistically significant. The correlation graphs had similar curves in both gender groups and both age groups. The parameters of the total HRV, as well as the activity of the parasympathetic nervous system (PNS), exhibited similar growth trends with age, with a peak increase in their values at 8 and 9 years of age. HR, as well as the activity of the sympathetic nervous system (SNS), decreased with age. Gender differences also followed a consistent pattern: parameters characterizing the activity of the peripheral nervous system were significantly higher in boys than in girls across all age groups.

Schilder F.P., de Weijer A.D., Levels K., Bruinsma B., Geuze E.

Song Y., Sun Z., Luo F., Yu B.

Mason M.A., Briefer E.F., Semple S., McElligott A.G.

Positive welfare is a relatively modern concept based on the idea that on the whole, an animal’s positive experiences should outweigh their negative ones. Intuitively, we therefore require indicators to measure when animals are experiencing positive and negative emotional states, as well as providing opportunities for animals to create positive experiences. Goats typically live rich social and emotional lives, are naturally inquisitive, and seek cognitive challenges, highlighting the importance of a complex and cognitively stimulating environment for their welfare. However, how goats respond to their environment is not the same for each individual, underlining the shortcomings of a ‘one size fits all’ approach to enhancing welfare. In sum, to achieve positive welfare in goats, we must possess a means to monitor their emotional experiences, understand their cognitive abilities and provide sufficient opportunities to apply these, while ensuring welfare measures are tailored at an individual level. This chapter will therefore focus on potential behavioural, physiological, and cognitive indicators used to measure goat emotional states in the short and long term; their cognitive abilities in the physical and social domains; and the effect of personality on how goats interact with their social environment and on cognitive abilities. It contains enriching material in the form of videos and goat call recordings to complement your reading experience.

Guillet A., Argoul F.

Sun Y., Zhang X., Xue H.

Burks J.H., Bruce L.K., Kasl P., Soltani S., Viswanath V., Hartogensis W., Dilchert S., Hecht F.M., Dasgupta S., Altintas I., Gupta A., Mason A.E., Smarr B.L.

AbstractIn tasks involving human health condition data, feature selection is heavily affected by data types, the complexity of the condition manifestation, and the variability in physiological presentation. One type of variability often overlooked or oversimplified is the effect of biological sex. As females have been chronically underrepresented in clinical research, we know less about how conditions manifest in females. Innovations in wearable technology have enabled individuals to generate high temporal resolution data for extended periods of time. With millions of days of data now available, additional feature selection pipelines should be developed to systematically identify sex-dependent variability in data, along with the effects of how many per-person data are included in analysis. Here we present a set of statistical approaches as a technique for identifying sex-dependent physiological and behavioral manifestations of complex diseases starting from longitudinal data, which are evaluated on diabetes, hypertension, and their comorbidity.

Daniel‐Watanabe L., Cook B., Leung G., Krstulović M., Finnemann J., Woolley T., Powell C., Fletcher P.

AbstractPhysiological regulation strategies can be effective in reducing anxiety. However, while these strategies are often learned and practised under low‐stress conditions, they are more likely to be required under conditions of high stress. We created virtual reality (VR) biofeedback games to both teach participants a breathing technique and then practise that technique under stress. We present two studies: the first provides a proof of concept, demonstrating that participants can apply the breathing technique during stress, with a significant lowering of both respiration rate and increase in heart rate variability (HRV) under stress (p < .001). The second study explicitly evaluated the effectiveness of training by comparing trained and untrained groups. Training was associated with a significantly greater HRV (p = .008) under stress. In within‐group comparisons of HRV during stress compared to a baseline stressor presented before training, the trained group showed a significantly greater increase compared to untrained controls (p = .025). Our results show the feasibility and potential effectiveness of VR‐based games for biofeedback training under experimentally applied stress. This may offer the opportunity for clinical techniques to more closely reflect the circumstances under which those techniques will be required.

de Almeida-Neto P.F., de Oliveira F.C., de Oliveira-Júnior J.M., Medeiros Alves J.C., Rocha M., Medeiros da Silva I., Câmara-Rocha R.F., Silva Dantas P.M., de Araújo Tinôco Cabral B.G.

Previously, it was suggested that biological maturation (BM) could be linked to cardiac autonomic recovery (CAR) in the pediatric population. However, this influence hasn’t been confirmed yet. Our aim was to investigate the impact of BM on CAR in female volleyball players. Experimental study with a sample of 38 volleyball players, comprising 20 girls (age: [11.6 ± 2.1] years) and 18 women (age: [24.5 ± 5.5] years), we analyzed BM, comparing maturing subjects (girls) with mature subjects (women). Additionally, we assessed peak height velocity (PHV) in girls. We conducted a training session involving repeated sprints (3 rounds of 6 sprints interspersed by 5 min [min] of passive rest). Using short-range radio telemetry, we analyzed CAR during (at the end of the 1st and 2nd rounds) and after (following the 3rd round) the training session of repeated sprints by applying the 60-s to 300-s heart rate recovery index (HRR-Index). Girls exhibited superior CAR compared to women (round 2: 60-s, 120-s, 240-s, and 300-s, p < 0.005). Subgroup analyses of BM indicated that individuals in the Late-PHV stage demonstrated superior CAR compared to those in the Early-PHV and During-PHV groups. (60-s to 300-s, η2p > 0.4, p < 0.05). Subjects in the During-PHV stage were superior to those in the Early-PHV stage (240-s á 300-s, η2 p > 0.4, p < 0.05). We have concluded that biological maturation has a significant impact on cardiac autonomic recovery.

Sentis A.I., Rasero J., Gianaros P.J., Verstynen T.D.

AbstractResting heart rate may confer risk for cardiovascular disease (CVD) and other adverse cardiovascular events. While the brainstem's autonomic control over heart rate is well established, less is known about the regulatory role of higher level cortical and subcortical brain regions, especially in humans. This study sought to characterize the brain networks that predict variation in prevailing heart rate in otherwise healthy adults. We used machine learning approaches designed for complex, high‐dimensional data sets, to predict variation in instantaneous heart period (the inter‐heartbeat‐interval) from whole‐brain hemodynamic signals measured by fMRI. Task‐based and resting‐state fMRI, as well as peripheral physiological recordings, were taken from two data sets that included extensive repeated measurements within individuals. Our models reliably predicted instantaneous heart period from whole‐brain fMRI data both within and across individuals, with prediction accuracies being highest when measured within‐participants. We found that a network of cortical and subcortical brain regions, many linked to visceral motor and visceral sensory processes, were reliable predictors of variation in heart period. This adds to evidence on brain–heart interactions and constitutes an incremental step toward developing clinically applicable biomarkers of brain contributions to CVD risk.

Keur-Huizinga L., Huizinga N.A., Zekveld A.A., Versfeld N.J., van de Ven S.R., van Dijk W.A., de Geus E.J., Kramer S.E.

In recent studies, psychophysiological measures have been used as markers of listening effort, but there is limited research on the effect of hearing loss on such measures. The aim of the current study was to investigate the effect of hearing acuity on physiological responses and subjective measures acquired during different levels of listening demand, and to investigate the relationship between these measures. A total of 125 participants (37 males and 88 females, age range 37-72 years, pure-tone average hearing thresholds at the best ear between -5.0 to 68.8 dB HL and asymmetry between ears between 0.0 and 87.5 dB) completed a listening task. A speech reception threshold (SRT) test was used with target sentences spoken by a female voice masked by male speech. Listening demand was manipulated using three levels of intelligibility: 20 % correct speech recognition, 50 %, and 80 % (IL20 %/IL50 %/IL80 %, respectively). During the task, peak pupil dilation (PPD), heart rate (HR), pre-ejection period (PEP), respiratory sinus arrhythmia (RSA), and skin conductance level (SCL) were measured. For each condition, subjective ratings of effort, performance, difficulty, and tendency to give up were also collected. Linear mixed effects models tested the effect of intelligibility level, hearing acuity, hearing asymmetry, and tinnitus complaints on the physiological reactivity (compared to baseline) and subjective measures. PPD and PEP reactivity showed a non-monotonic relationship with intelligibility level, but no such effects were found for HR, RSA, or SCL reactivity. Participants with worse hearing acuity had lower PPD at all intelligibility levels and showed lower PEP baseline levels. Additionally, PPD and SCL reactivity were lower for participants who reported suffering from tinnitus complaints. For IL80 %, but not IL50 % or IL20 %, participants with worse hearing acuity rated their listening effort to be relatively high compared to participants with better hearing. The reactivity of the different physiological measures were not or only weakly correlated with each other. Together, the results suggest that hearing acuity may be associated with altered sympathetic nervous system (re)activity. Research using psychophysiological measures as markers of listening effort to study the effect of hearing acuity on such measures are best served by the use of the PPD and PEP.

Ritz T.