Changes In Cardiac Vagal Tone Research Articles

Short-Term Effects of Heart Rate Variability Biofeedback on Working Memory.

Drawing upon the well-documented impact of long-term heart rate variability biofeedback (HRVB) on psychophysiological responses, this study seeks to explore the short-term effects arising from a single HRVB session during and after paced breathing exercise. The research aligns with the neurovisceral integration model, emphasizing the link between heart rate variability (HRV) levels and cognitive performance. Therefore, a randomized controlled trial employing a between-subjects design was conducted with 38 participants. Each participant was assigned to either the paced breathing intervention group or the spontaneous breathing control group. The study assessed various parameters such as cardiac vagal tone, evaluated through vagally mediated HRV measures, and working memory, measured using the N-back task. Additionally, participants' affective states were assessed through self-reported questionnaires, specifically targeting attentiveness, fatigue, and serenity. The results notably reveal enhancements in the working memory task and an elevated state of relaxation and attention following the HRVB session, as evidenced by higher averages of correct responses, serenity and attentiveness scores. However, the findings suggest that this observed improvement is not influenced by changes in cardiac vagal tone, as assessed using a simple mediation analysis. In conclusion, this study presents promising insights into the impact of a single HRVB session, laying the foundation for future research advancements in this domain.

Can PTSD be prevented? A novel approach to increasing physiological resilience: a pilot study.

Much of the U.S. adult population will experience a traumatic event at some point in their lives, resulting in about 20 million people developing posttraumatic stress disorder (PTSD) and costing over $143 billion for healthcare. The Community Resilience Model (CRM) and Mental and Emotional Self-Management (MESM) are potential novel solutions for stemming the tide of PTSD diagnoses resulting from a traumatic event. This pilot study was conducted to examine the phasic and tonic changes in cardiac vagal tone in a non-traumatized sample population (N = 83) after a 1-week intervention. Group comparisons were conducted between the CRM (n = 26), MESM (n = 34), and Control (n = 23) conditions. Participants ranged in age from 18 to 30. A phasic effect on cardiac vagal tone was found for the MESM condition within subjects but not for the CRM or control conditions. A tonic effect on cardiac vagal tone was not found within subjects amongst the three conditions. The phasic effect in the MESM condition was significantly different between itself and the CRM and control groups. No tonic effects on cardiac vagal tone were found between conditions either. These results suggest cardiac vagal tone responds to focused breathing in the moment only, but more research with larger sample sizes, longer intervention duration, and better methods to track home practice compliance are needed before one accepts the insignificant results as valid. This pilot study can serve as an introduction to the study of physiological processes that might be trainable to increase resilience in non-traumatized populations and serve as a springboard for future studies of physiological resilience to traumatic stress.

Dynamic fluctuations in maternal cardiac vagal tone moderate moment-to-moment associations between children's negative behavior and maternal emotional support.

Our primary objective was to examine the extent to which moment-to-moment associations between preschool-aged children's behavior and maternal emotional support differed for mothers showing different levels of parasympathetic engagement. We used behavioral observations of maternal and child behavior and maternal changes in cardiac vagal tone assessed via respiratory sinus arrhythmia in 15-s intervals during a 5-min challenging puzzle task (N = 121 dyads; 65 girls, Mage = 4.42 years). Results from multilevel models showed that increases in children's defeat (e.g., frustration, task withdrawal) coupled with maternal vagal augmentation (an index of social engagement) in a given 15-s interval predicted increases in maternal support in the next interval, whereas increases in children's defeat coupled with maternal vagal withdrawal (an index of physiological arousal) in a given 15-s interval did not predict increases in maternal support. Findings suggest that vagal augmentation in mothers may operate together with fluctuations in children's negative behaviors to predict supportive parenting in real time. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

The Physiological Regulation of Emotion During Social Interactions: Vagal Flexibility Moderates the Effects of a Military Parenting Intervention on Father Involvement in a Randomized Trial.

To make prevention programs more effective and understand "what works for whom," evidence regarding what individual characteristics predict intervention responsiveness is needed. Previous studies have evaluated a military parent training program known as After Deployment Adaptive Parenting Tools/ADAPT, yet less is understood about the program's varying effects for fathers. We tested the physiological regulation of emotion during social interactions as a moderator predicting fathers' responsiveness in a randomized trial of ADAPT, in which emotion regulation was operationally measured through vagal flexibility (VF; dynamic changes in cardiac vagal tone). Families with a child aged between 4 and 13years for whom physiological data were gathered (n = 145) were randomly assigned to ADAPT (14-week face-to-face group intervention) or a control group (services as usual). Fathers in these families were National Guard/Reserve members who had been deployed to war in Iraq and/or Afghanistan and recently returned. Prior to the intervention, cardiac data was collected in-home throughout a set of family interaction tasks and VF was operationalized as the changes in high frequency (HF) power of heart rate variability (HRV) from a reading task to a problem-solving task. Parenting behaviors were observed and coded based on theory-driven indicators pre-intervention and at 1-year follow-up. Results of structural equation modeling showed that VF significantly moderated fathers' intervention responsiveness, such that fathers with higher vs. lower VF exhibited more effective parenting at 1-year follow-up if they were randomized into ADAPT vs. the control group. This study is the first to demonstrate that parasympathetic vagal functioning may be a biomarker to predict response to a military parenting intervention to enhance parenting in combat deployed fathers. The implications for precision-based prevention are discussed.

Changes in cardiac vagal tone as measured by heart rate variability during naloxone-induced opioid withdrawal

BackgroundHeart rate variability (HRV) is of interest to researchers due to its potential utility as a marker for both physiological and psychological stress. Sympatholytics are used to treat opioid withdrawal, but little information about the parasympathetic system’s role in mediating withdrawal symptoms exists. The goal of the current study was to evaluate changes in HRV during opioid withdrawal to provide a better understanding of the autonomic effects of opioid withdrawal. MethodsTen male participants (mean age = 46.4 years) received intramuscular naloxone (mean dose =0.26 mg) to confirm opioid dependence. The presence and severity of withdrawal symptoms were assessed using subjective and objective measures (Wang et al., 1974). Electrocardiography (ECG) was measured continuously, and HRV was analyzed in 2-minute segments before naloxone injection (at baseline) and after participants were in moderate withdrawal (Wang Test score ≥10). Heart rate, blood pressure, pupil diameter, and respiratory rate were also examined. ResultsPupil diameter significantly increased after naloxone administration relative to baseline (t(9) = 5.562, p = 0.000). Both high frequency (HF) HRV (Z = -2.803, p = 0.005) and root mean square of successive differences (RMSSD) HRV (Z = -2.090, p = 0.037) were significantly lower during withdrawal relative to baseline. Increases in heart rate (Z = -2.090, p = 0.032) and systolic pressure (t(9) = 8.099, p = 0.0000) from baseline to withdrawal also were significant. ConclusionsThese preliminary data indicate that a large reduction in cardiac vagal tone occurs during naloxone-induced withdrawal. This finding underscores the need for further research into the role of the parasympathetic nervous system in opioid withdrawal.

Heart rate variability as a marker of healthy ageing

BackgroundWith population ageing a significant concern, modifiable factors contributing to healthy ageing must be identified. Autonomic responding reflected by heart rate variability (HRV) has well-established links to general health and wellbeing in younger populations; but has yet to be explored in older individuals. MethodsForty-five healthy participants (49–82 years old) completed questionnaires about sleep and physical and psychological health. Autonomic activity was measured during rest and whilst completing a computerised battery of cognitive tasks. Participants then wore an ambulatory heart rate monitor overnight, and recorded their sleep and physical activity for one week. HRV parameters reflecting cardiac vagal tone were derived from electrocardiograph recordings. ResultsAge and resting HRV were not related; however a positive association was identified between higher HRV in the 2 h prior to sleep and older age. Higher resting HRV, older age, and better sleep quality significantly predicted psychological wellbeing; and fewer somatic and physical health symptoms and older age predicted better average sleep quality ratings. Older age and poorer general health were significant predictors of cognitive performance deficits. ConclusionThese findings suggest that an age-related decline in HRV is not inevitable. Longitudinal designs exploring within-individual changes in cardiac vagal tone are required to better understand the factors contributing to healthy ageing.

Inconsistent relation of nonlinear heart rate variability indices to increasing vagal tone in healthy humans.

Prior work has found that linear heart rate variability (HRV) indices do not accurately reflect cardiac vagal control, and nonlinear indices of HRV have been proposed as alternative tools that may better capture cardiac vagal effects. We used progressive low dose atropine to induce changes in cardiac vagal tone to test the hypotheses that nonlinear HRV indices accurately reflect cardiac vagal control, and that their changes in response to low dose atropine correlate with those in RR interval. Changes in RR interval and HRV indices during intravenous injections of saline (control) and 6 cumulative doses of atropine (from 1.4 to 7.2 μg/kg) during controlled breathing at 15 breaths per minute were assessed in 14 young healthy individuals. As expected, low dose atropine increased average RR interval (vagotonic effect). There was no strong association between vagotonic changes in RR interval and the majority of nonlinear HRV indices, either within or among subjects. These data suggest an inconsistent relationship between responses of nonlinear HRV indices and RR interval to changes in cardiac vagal tone. Therefore, nonlinear HRV indices may not be reliable indices of cardiac vagal control in healthy humans.

Postprandial cardiac vagal tone and transient lower esophageal sphincter relaxation (TLESR)

Transient lower esophageal sphincter relaxation (TLESR) is a vagally mediated reflex that occurs most frequently after a meal. Cardiac vagal tone (CVT) decreases after a meal, and correlates with changes in gastric electrical activity. Furthermore, decreased CVT has been reported in patients with gastro-esophageal reflux disease. We therefore aimed to characterize the association between postprandial changes in CVT and the occurrence of TLESR and reflux. Ten healthy volunteers underwent simultaneous autonomic nervous system, gastric myoelectric activity, lower esophageal-sphincter pressure, and reflux monitoring for 30min in the fasting state, followed by a standard meal, and a further 4h postprandially. Results are in mean±SEM. The number of TLESRs (P<0.0001) and reflux episodes (P<0.0001) increased after the meal, while CVT decreased (P<0.01). Cardiac sensitivity to baroreceptor reflex (CSB) showed similar time course changes to CVT (P=0.06). During the first postprandial hour there was a strong correlation between the number of TLESRs and reflux episodes with CVT (R(2) =0.51 and R(2) =0.50, respectively; P<0.05). There was also an increase in the dominant power and power ratio on electrogastrography (P<0.05) after the meal. In healthy volunteers, the increase in the number of TLESRs and reflux episodes after a meal occurred mostly at a time of reduced CVT. Further studies should explore whether modulation of CVT can modify frequency of TLESRs and also this relationship should be further explored in patients with reflux disease.

A Theoretical Appraisal of the Dependence of Respiratory Sinus Arrhythmia on Gradual Vagal Blockade

The high frequency (HF) indices of heart rate variability (HRV), which reflect the magnitude of respiratory sinus arrhythmia (RSA), have been repeatedly used as measures of cardiac vagal tone. Recent studies, however, have shown experimentally that variations in these indices do not necessarily reflect proportional changes in cardiac parasympathetic outflow. The goal of this study was to obtain a physiological-based theoretical evaluation of the relationship between RSA and cardiac vagal tone, which will help explain conflicting experimental results previously published. We derived a theoretical model for heart rate (HR) response to gradual vagal blockade. The model implements the integral-pulse-frequency-modulation (IPFM) approach to sinoatrial (SA) node physiology. The level of vagal blockade was simulated by the addition of a cardio-selective muscarinic antagonist. The derivations of the model lead to a closed set of equations, from which the dependence of the HF indices on the level of vagal blockade is deduced. It is shown that several aspects of the physiological condition may have a substantial effect on this relationship: the level of baseline vagal activity, the relationship between vagal tone and the fluctuations in its traffic, the level of sympathetic activity, etc em leader Hence, changes in the HF indices of HRV provide a plausible assessment of the changes in cardiac vagal tone only under a specific range of physiological conditions.

Therapeutic Effects of Imipramine Are Counteracted by Its Metabolite, Desipramine, in Patients With Generalized Anxiety Disorder

Imipramine has been shown to reduce anxiety in patients with generalized anxiety disorder (GAD). However, some properties of imipramine may diminish or counteract its anxiolytic effects. The authors previously found that the greater the reduction in cardiac vagal control after 6 weeks of imipramine treatment, the smaller the improvement in anxiety-related symptoms. The purpose of this study was to determine whether the authors' previous findings were replicable and to gather information on the plasma levels of imipramine, desipramine (the major metabolite of imipramine), and anticholinergic levels. Fourteen patients with GAD were administered imipramine for 6 weeks. Their scores from self-administered and investigator-administered rating scales were obtained before and after the treatment, and the changes in these scores were contrasted with the changes in cardiac vagal tone, along with the absolute plasma levels of imipramine, desipramine, and anticholinergic activity at the end of week 6. The authors observed a greater improvement in symptoms of anxiety in those who showed the smallest decreases in cardiac vagal tone and in those who showed the smallest increases in desipramine and anticholinergic plasma levels. Moreover, strong relationships were observed between desipramine and anticholinergic levels. These results demonstrate that imipramine not only has therapeutic effects, but it may also have properties that result in physiologic states that counteract its therapeutic effects. Future research should investigate the direct anticholinergic effects of desipramine and determine whether there is a parallel between the anticholinergic effects and the clinical outcome of other pharmacologic treatments, including antidepressants with predominantly norepinephrine or serotonin reuptake inhibitory properties.

Effects on hypoxaemia on foetal heart rate, variability and cardiac rhythm.

1. Experiments were carried out in 30 chronically catheterized foetal sheep (128-144 days; term 150 days) and in seven of these foetuses before, during and after acute hypoxaemia. The extent to which changes in sympathoadrenal activity and cardiac vagal activity affected the foetal cardiac response to hypoxaemia was measured. Three measurements were used: foetal heart rate (FHR), heart rate variability (HRV; measured as the coefficient of variation in pulse interval) and power spectral density (PSD; measured over the frequency ranges of 0.04-1.3 Hz). Cardiac vagal activity was blocked by atropine, beta-adrenoceptor activity was blocked by propranolol. 2. Under normoxaemic conditions, cardiac vagal blockade caused a rise in mean arterial pressure (MAP; P < 0.001), an increase in FHR (P < 0.001), a decrease in HRV (P < 0.001) and a decrease in PSD (P < 0.001). beta-adrenoceptor blockade caused a rise in MAP (P < 0.001), a fall in FHR (P < 0.01), a decrease in HRV (P < 0.001) but no change in PSD. 3. During mild hypoxaemia (PO2 = 12-14.5 mmHg) and moderate hypoxaemia (PO2 = 10-11.9 mmHg), foetal MAP (P < 0.001, P< 0.001), HRV (P < 0.01, P < 0.001) and PSD in the frequency range 0.04-0.45 Hz increased (P < 0.05-P < 0.001). Foetal heart rate decreased when foetuses became moderately hypoxaemic (P < 0.001). 4. After cardiac vagal blockade, hypoxaemia was associated with an increase in FHR compared with non-blocked hypoxaemic foetuses (P < 0.01, P < 0.001). The increase in HRV was abolished (P < 0.001, P < 0.001) as was the increase in PSD (P < 0.01-P < 0.001). 5. After beta-adrenoceptor blockade, the bradycardia that occurred during hypoxaemia was enhanced (P < 0.01, P < 0.05), the increase in HRV was not affected and neither was the increase in PSD. 6. As FHR and HRV of normoxaemic foetal sheep were affected both by atropine and propranolol, it would seem that both cardiac vagal and sympathoadrenal activity modulate the foetal heart under resting conditions. The lack of any effect of beta-adrenoceptor blockade on PSD under these conditions suggests that power spectral analysis (PSA) is not as sensitive as the other two methods in detecting sympathetically mediated modulation of the heart. 7. Because the hypoxaemia induced bradycardia and increase in HRV and in PSD were abolished by atropine (P < 0.01-P < 0.001), it is concluded that during hypoxaemia foetal HRV is mainly modulated by changes in cardiac vagal tone. Propranolol had no effect on foetal HRV, although it reduced it under normoxaemic conditions; therefore, it is concluded that cardiac sympathetic neural activity was not increased in acute hypoxaemia uncomplicated by acidosis. However, there was strong evidence of increased sympathoadrenal tone on the foetal heart in hypoxaemia, that is, there was a rise in FHR in hypoxaemic atropinized foetuses and a greater fall in FHR in beta-adrenoceptor blocked hypoxaemic foetuses. Therefore, this increased sympathetic influence on the foetal heart during hypoxaemia must be predominantly the result of increased adrenomedullary secretion of catecholamines. 8. Maintenance of foetal cardiac output depends on the chronotropic and ionotropic effects of catecholamines. Therefore, this adrenomedullary influence on the foetal heart during hypoxaemia is important to offset the opposing effects of increased cardiac vagal tone.

Infant Temperament and Cardiac Vagal Tone: Assessments at Twelve Weeks of Age

Sixty 12-week-old infants participated in a laboratory study to explore the relations between temperament and cardiac vagal tone. Temperament was evaluated via laboratory observations and maternal ratings. Cardiac vagal tone, measured as the amplitude of respiratory sinus arrhythmia, was quantified from beat-to-beat heart period data collected during a resting baseline period and during the laboratory assessment of temperament. Specific hypotheses were investigated relating temperament to both basal cardiac vagal tone and changes in cardiac vagal tone during social/attention challenges. Infants with higher baseline cardiac vagal tone were rated in the laboratory as showing fewer negative behaviors and were less disrupted by the experimental procedure. Infants who decreased cardiac vagal tone during the laboratory assessment were rated on maternal report temperament scales as having longer attention spans, and being more easily soothed.

Vasopressin-induced changes in cardiac vagal tone and oxygen consumption in dogs.

Experiments were conducted in 63 dogs to determine whether stimulation of vagal tone contributes to the decrease in O2 consumption (VO2) that results from arginine vasopressin (AVP) administration. Vagal stimulation with pilocarpine did not reduce VO2 in conscious dogs. In anesthetized dogs, bilateral electrical cervical efferent vagal stimulation lowered both cardiac output (CO; by 46%) and VO2 (by 22%) over the first 5 min. Between 7 and 11 min of stimulation, CO remained decreased, but VO2 returned to control. Significant increases in left atrial pressure, bradycardia, and a fall in mean arterial pressure accompanied vagal stimulation. All these effects of cervical vagal stimulation were abolished by cardiac denervation and also by pacing. Administration of a selective AVP V1 agonist led to significant reductions of CO and VO2. Cardiac denervation prevented the decrease in VO2 induced by AVP infusion, but not the decrease in CO. During AVP infusions, pacing at a rate slightly higher than control heart rate did not prevent the fall in CO or in VO2, whereas pacing at 150 beats/min prevented part of the fall in VO2. Sinoaortic denervation or atropine treatment prevented the decrease in VO2 resulting from AVP infusion. The combination of alpha- and beta-blockade did not affect the CO or the VO2 response to AVP infusion, nor did naloxone treatment. The administration of atrial or ventricular extracts, but not that of alpha-human atrial natriuretic peptide, led to a significant reduction in VO2. These results are compatible with the hypothesis that AVP infusion increases vagal tone to the heart, which, possibly as a result of increased left atrial pressure and reduced heart rate, may release a factor reducing VO2.

Prediction of Tonic Parasympathetic Cardiac Control Using Respiratory Sinus Arrhythmia: The Need for Respiratory Control

Respiratory sinus arrhythmia (RSA) has received much attention in recent years due to the large body of evidence indicating that variations in this phenomenon represent alterations in parasympathetic cardiac control. Although it appears that respiratory sinus arrhythmia is mediated by vagal mechanisms, the extent to which the well-known respiratory influences (i.e., rate and tidal volume) on respiratory sinus arrhythmia (in altering its magnitude) may moderate the relationship between RSA and cardiac vagal tone has never been systematically studied. We addressed this issue by examining intraindividual relationships among RSA magnitude, respiration (rate and tidal volume), and heart period among six healthy male adults after intravenous administration of 10 mg propranolol, a beta-adrenergic blocker. Subjects were exposed to various behavioral tasks which altered all physiological variables measured. Variations in heart period after beta blockade were assumed to be predominantly vagally mediated. Within-subject regression analyses consistently showed that respiratory parameters influenced RSA magnitude, but not tonic variations in beta-blocked heart period, suggesting that respiratory-mediated RSA alterations are not associated with changes in cardiac vagal tone. Only when respiratory variables were statistically controlled was there evidence of a reasonable correspondence between beta-blocked heart period and RSA amplitude, providing support for the idea that respiratory parameters need to be controlled when using RSA amplitude as an index of cardiac vagal tone. Repeated-measures analyses of variance of mean levels of heart period and respiratory sinus arrhythmia across subjects supplemented and supported the intraindividual results. These findings point to the importance of controlling for respiratory parameters when using respiratory sinus arrhythmia as a cardiac vagal index.

Vagal Responsiveness to Gavage Feeding as an Index of Preterm Status

Vagal responsivity to orogastric stimulation is necessary for gastrointestinal function and may reflect autonomic regulation. Our study evaluated vagal responsivity during gavage feeding as an index of preterm clinical status. Vagal and behavioral responsivity of 26 preterm infants during gavage feeding was measured. Vagal tone was quantified with a noninvasive measure (vagal tone index) developed by Porges (Porges SW: U.S. patent 4,510.944, 1985), which extracts a valid measure of cardiac vagal tone from the ECG. The study investigated whether vagal tone changed during gavage feeding and whether individual differences in the vagal tone response pattern were related to clinical outcome. Infants who demonstrated an increase in vagal tone during feeding and a decrease after feeding had significantly shorter hospitalizations. This effect was independent of weight gain trajectories. Baseline levels of vagal tone were positively associated with subsequent weight gain. Traditional risk measures did not predict length of hospitalization independently of gestational age. This study represents the first documentation that small changes in cardiac vagal tone during gavage feeding, previously imperceptible to clinicians and researchers, may be quantitatively extracted from the ECG and provide an important index of clinical status.

Dynamic changes in cardiac vagal tone as measured by time-series analysis

A time-series analysis of heart rate variability was evaluated as a marker of cardiac vagal tone using well-characterized autonomic interventions. Heart period (R-R interval) was recorded in 14 mongrel dogs from which the amplitude of the respiratory sinus arrhythmia (0.24-1.04 Hz) was determined. Exercise elicited significant (P less than 0.01) reductions in the index of vagal tone (control 6.3 +/- 0.3 ln ms2 vs. exercise 2.4 +/- 0.4 ln ms2) that were accompanied by significant (P less than 0.01) increases in heart rate (control 123.1 +/- 5 vs. exercise 201.0 +/- 7.7 beats/min). The vagal tone index remained greater than 0 throughout exercise. After propranolol HCl pretreatment, the vagal tone index rapidly decreased toward zero (control 6.2 +/- 0.5; exercise 0.7 +/- 0.3 ln ms2), despite significantly lower increases in heart rate (control 109.3 +/- 4.2; exercise 178.0 +/- 7.6 beats/min). Atropine given during exercise evoked significantly greater increases in heart rate in the control (+48.7 +/- 7.9 beats/min) vs. propranolol (+14.2 +/- 6.7 beats/min) conditions. These data suggest that 1) high levels of cardiac vagal tone remain during exercise; 2) vagal withdrawal is largely responsible for the heart rate increase after beta-adrenergic receptor blockade; and 3) time-series analysis of the R-R interval can provide a dynamic and noninvasive index of cardiac vagal tone.