Measure Of Cardiac Vagal Tone Research Articles

Sleep and Daily Positive Emotions – Is Heart Rate Variability a Mediator?

Abstract. Sleep quality is considered a basic dimension of emotional health. The psychophysiological mechanisms underlying the associations between sleep quality and positive emotions are still largely unknown, yet autonomic regulation may play a role. This study employed a two-day ecological momentary assessment methodology in a sample of young adults to investigate whether subjective sleep quality reported in the morning was associated with daily positive emotional experience and whether this association was mediated by heart rate variability (HRV), a measure of cardiac vagal tone. Sleep quality was assessed using an electronic sleep diary upon awakening, while resting HRV and positive emotions were inspected at random times throughout the day using photoplethysmography and an electronic diary, respectively. Relevant confounding variables such as smoking, alcohol intake, and physical exercise between each measurement were also assessed. The sample included 121 participants (64.8% females, Mage = 25.97 ± 5.32 years). After controlling for relevant confounders including health behaviors and psychiatric comorbidities, mediation analysis revealed that greater sleep quality positively predicted daily HRV (β = .289, p < .001) which, in turn, had a direct influence on positive emotions (β = .244, p = .006). Also, sleep quality directly predicted positive emotional experience (β = .272, p = .001). Lastly, the model showed an indirect effect between sleep quality and positive emotions via HRV (β = .071, 95% BCI [.011, .146]). Results support the view of HRV as a process variable linking sleep to positive emotions. Experimental data is needed to consolidate the present findings.

SPECIAL ISSUE: Do Biofeedback, Neurofeedback, and Neuromeditation Have a Role in Psychedelic-Assisted Therapies?

SPECIAL ISSUE: Do Biofeedback, Neurofeedback, and Neuromeditation Have a Role in Psychedelic-Assisted Therapies?

Development of mother-infant co-regulation: The role of infant vagal tone and temperament at 6, 9, and 12 months of age

Using Porges’ (2011) Polyvagal Theory as a backdrop, this study examined whether changes in parasympathetic functioning, as indexed by baseline measures of cardiac vagal tone at 6, 9, and 12 months of age, were linked to changes in infants’ (N = 101) dyadic co-regulation over these same time points. Mothers and infants were observed at each time point during a 15-minute unstructured free-play and co-regulated patterns of interactions were coded using the Revised Relational Coding System (Fogel et al., 2003). Analyses were carried out using multi-process growth curve modeling to examine baseline measurements (intercepts) and changes (slopes) in vagal tone, co-regulation as well as mothers’ report of infant temperament. Findings demonstrate links between infants’ vagal tone and changes in mother-infant co-regulation. Specifically, increasing levels of cardiac vagal tone was related to increases in symmetrical but decreases in unilateral patterns of co-regulation over time. These findings suggest that changes in the autonomic nervous system likely undergird infants’ improving capacity to engage in more mutually sustained patterns of co-regulation.

Different Impact of Heart Rate Variability in the Deep Cerebral and Central Hemodynamics at Rest: An in silico Investigation.

Background: Heart rate variability (HRV), defined as the variability between consecutive heartbeats, is a surrogate measure of cardiac vagal tone. It is widely accepted that a decreased HRV is associated to several risk factors and cardiovascular diseases. However, a possible association between HRV and altered cerebral hemodynamics is still debated, suffering from HRV short-term measures and the paucity of high-resolution deep cerebral data. We propose a computational approach to evaluate the deep cerebral and central hemodynamics subject to physiological alterations of HRV in an ideal young healthy patient at rest.Methods: The cardiovascular-cerebral model is composed by electrical components able to reproduce the response of the different cardiovascular regions and their features. The model was validated over more than thirty studies and recently exploited to understand the hemodynamic mechanisms between cardiac arrythmia and cognitive deficit. Three configurations (baseline, increased HRV, and decreased HRV) are built based on the standard deviation (SDNN) of RR beats. For each configuration, 5,000 RR beats are simulated to investigate the occurrence of extreme values, alteration of the regular hemodynamics pattern, and variation of mean perfusion/pressure levels.Results: In the cerebral circulation, our results show that HRV has overall a stronger impact on pressure than flow rate mean values but similarly alters pressure and flow rate in terms of extreme events. By comparing reduced and increased HRV, this latter induces a higher probability of altered mean and extreme values, and is therefore more detrimental at distal cerebral level. On the contrary, at central level a decreased HRV induces a higher cardiac effort without improving the mechano-contractile performance, thus overall reducing the heart efficiency.Conclusions: Present results suggest that: (i) the increase of HRV per se does not seem to be sufficient to trigger a better cerebral hemodynamic response; (ii) by accounting for both central and cerebral circulations, the optimal HRV configuration is found at baseline. Given the relation inversely linking HRV and HR, the presence of this optimal condition can contribute to explain why the mean HR of the general population settles around the baseline value (70 bpm).

Higher resting heart rate variability predicts skill in expressing some emotions.

Vagally mediated heart rate variability (vmHRV) is a measure of cardiac vagal tone, and is widely viewed as a physiological index of the capacity to regulate emotions. However, studies have not directly tested whether vmHRV is associated with the ability to facially express emotions. In extending prior work, the current report tested links between resting vmHRV and the objectively assessed ability to facially express emotions, hypothesizing that higher vmHRV would predict greater expressive skill. Eighty healthy women completed self-reported measures, before attending a laboratory session in which vmHRV and the ability to express six emotions in the face were assessed. A repeated measures analysis of variance revealed a marginal main effect for vmHRV on skill overall; individuals with higher resting vmHRV were only better able to deliberately facially express anger and interest. Findings suggest that differences in resting vmHRV are associated with the objectively assessed ability to facially express some, but not all, emotions, with potential implications for health and well-being.

Acute and chronic systemic CB1 cannabinoid receptor blockade improves blood pressure regulation and metabolic profile in hypertensive (mRen2)27 rats.

We investigated acute and chronic effects of CB1 cannabinoid receptor blockade in renin‐angiotensin system‐dependent hypertension using rimonabant (SR141716A), an orally active antagonist with central and peripheral actions. In transgenic (mRen2)27 rats, a model of angiotensin II‐dependent hypertension with increased body mass and insulin resistance, acute systemic blockade of CB1 receptors significantly reduced blood pressure within 90 min but had no effect in Sprague‐Dawley rats. No changes in metabolic hormones occurred with the acute treatment. During chronic CB1 receptor blockade, (mRen2)27 rats received daily oral administration of SR141716A (10 mg/kg/day) for 28 days. Systolic blood pressure was significantly reduced within 24 h, and at Day 21 of treatment values were 173 mmHg in vehicle versus 149 mmHg in drug‐treated rats (P < 0.01). This accompanied lower cumulative weight gain (22 vs. 42 g vehicle; P < 0.001), fat mass (2.0 vs. 2.9% of body weight; P < 0.05), and serum leptin (2.8 vs. 6.0 ng/mL; P < 0.05) and insulin (1.0 vs. 1.9 ng/mL; P < 0.01), following an initial transient decrease in food consumption. Conscious hemodynamic recordings indicate twofold increases occurred in spontaneous baroreflex sensitivity (P < 0.05) and heart rate variability (P < 0.01), measures of cardiac vagal tone. The beneficial actions of CB1 receptor blockade in (mRen2)27 rats support the interpretation that an upregulated endocannabinoid system contributes to hypertension and impaired autonomic function in this angiotensin II‐dependent model. We conclude that systemic CB1 receptor blockade may be an effective therapy for angiotensin II‐dependent hypertension and associated metabolic syndrome.

Implementation and Interpretation of Respiratory Sinus Arrhythmia Measures in Psychosomatic Medicine: Practice Against Better Evidence?

Respiratory sinus arrhythmia (RSA) or high-frequency heart rate variability has been widely used as a noninvasive measure of cardiac vagal tone. However, their dependency on both respiration rate and tidal volume is largely ignored. Only a minority of studies published in Psychosomatic Medicine in recent years has implemented precautions for controlling respiration rate in RSA measures, and tidal volume effects were only rarely addressed. We discuss methodologic issues related to respiratory control methods and present data that demonstrate that both respiration rate and tidal volume contribute substantially to the within-individual RSA variance under conditions of variable breathing, with tidal volume contributing up to one third beyond respiration rate. Finally, we outline a respiratory control method for the time-domain index of RSA and review research pertaining to its reliability, validity, and experimental application.

Longitudinal relations between child vagal tone and parenting behavior: 2 to 4 years.

The longitudinal relations between physiological markers of child emotion regulation and maternal parenting practices were examined from 2 to 4 years of age. At Time 1, cardiac vagal tone was assessed for one hundred four 2-year-olds (54 females); their mothers completed an assessment of parenting styles. Two years later, at Time 2, 84 of the original participants were reassessed on measures of cardiac vagal tone and parenting style. Results indicated both baseline cardiac vagal tone and maternal parenting practices to be stable from 2 to 4 years of age. Children's cardiac vagal tone predicted specific parenting practices from the toddler to preschool years. Further, child cardiac vagal tone moderated maternal restrictive-parenting practices from 2 to 4 years of age; mothers of children who were highly or moderately physiologically dysregulated were more likely to report restrictive parenting practices at both 2 and 4 years of age.

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.

Periodicity of a noninvasive measure of cardiac vagal tone during non-rapid eye movement sleep in non-sleep deprived and sleep-deprived normal subjects.

Cyclic alternating pattern (CAP) of microarousals reported in EEG studies is now regarded as an integrating mechanism for the different parts of the central nervous system including the autonomic system. A recently developed continuous index of cardiac parasympathetic activity (CIPA) can be time locked to the EEG allowing the relationship between EEG and autonomic changes to be studied in sleep. Eleven normal subjects were studied for evidence of periodicity in CIPA in non-REM sleep, five of whom had been sleep deprived. Fast Fourier's transformation of the CIPA data confirmed its periodicity with four frequency peaks in the range of 0.015 to 0.3 Hz. The frequency peaks previously reported as caused by respiration, Mayer waves and vasomotor thermoregulatory activity, were within what we called the alpha and beta rhythms of CIPA. There was an additional very slow peak not previously described and we called it the gamma rhythm. It covered the frequency range below 0.03 Hz. The gamma rhythm was the largest of all peaks in CIPA rhythms and its magnitude increased further in sleep-deprived subjects, but it invariably decreased during stage 4 sleep in both groups. Bursts of alpha waves in the EEG recorded concomitantly with CIPA in stage 1 sleep were associated with both peaks and troughs of the gamma rhythm. These results support previous proposals that cyclic alternating pattern in the EEG may be an integrating mechanism associated with functions of the central nervous system, and we have shown here its relationship with CIPA. Because cyclic alternating pattern can also be measured in CIPA, clinical exploitation of this phenomenon could include monitoring of epilepsy, studies of the effects of drug therapy, and assessment of other sleep disorders. All these are known to affect cyclic patterns of sleep EEG.

Real-time measurement of cardiac vagal tone in conscious dogs.

Rapid changes in heart rate are caused by changes in parasympathetic tone. The NeuroScope is an electronic device designed to offer an objective real-time measure of instantaneous cardiac vagal tone by phase demodulation of a high-resolution time domain of R-R wave intervals. Data are displayed against an arbitrary but linear scale, the cardiac index of parasympathetic activity (CIPA). To validate this method, 10 conscious healthy dogs were each given six incremental doses of atropine (0.01 mg/kg) to a total dose of 0.06 mg/kg or equal volumes of saline. A dose-response curve was constructed. At the maximum dose of atropine, CIPA values fell to 1. 3 +/- 0.7% (SD) of baseline, whereas R-R intervals fell to 51.5 +/- 11.5% of baseline, and standard deviation of the R-R wave interval fell to 10.6 +/- 6.5% of baseline. These findings show that the NeuroScope can provide a specific real-time index of cardiac vagal tone in dogs without need for recourse to atropine.

Toward a developmental model of child compliance: the role of emotion regulation in infancy.

The present study examined the relation between early emotion regulation and later compliance. When infants were 5, 10, and 18 months of age, they participated in a frustration task. The degree to which they reacted negatively to the stimuli and the behaviors they used to regulate that response were coded. Baseline heart rate also was recorded and a measure of cardiac vagal tone (VNA) was derived. Several tasks (electrode placement, toy clean-up, and test situation) were administered to elicit compliance/noncompliance when the participants were 30 months of age. Results revealed that infants who demonstrated low levels of regulatory behavior were more likely to be noncompliant as toddlers. Several interaction effects suggested that the prediction to later noncompliance was also dependent upon the infants' level of reactivity. Cardiac vagal tone also was related to compliance but in a contradictory fashion. High VNA was related to noncompliance to toy clean-up, whereas low VNA was related to noncompliance to electrode placement. The data provide support for a developmental model of compliance that includes the ability to regulate emotional arousal.

Physiological markers in early infancy: Stability of 1-to 6-month vagal tone

Twenty-six full-term infants were evaluated at 1-, 3-, and 6-months postpartum to explore the stability of Porges' (1985a) cardiac vagal tone index. One-month vagal tone (V̂) was not found to be associated with either 3- or 6-month measures of cardiac vagal tone, however, 3-month cardiac vagal tone was found to be predictive of 6-month cardiac vagal tone. Interestingly, 1-month heart period range was predictive of 6-month heart period range. These findings both replicate and extend previous research examining early patterns of development in cardiac indices.

Cardiac activity in infancy: Reliability and stability of individual differences

The goals of this study were to examine: (a) normative developmental changes in heart period and cardiac vagal tone: and (b) the reliability and stability over time of individual differences in the two measures. When the 73 infants participating in this short-term longitudinal study were 5, 7, 10, and 13 months old, a 5-min sample of cardiac activity was collected while the infants sat on thier mothers' laps in a quiet, attentive state. A second 5-min sample of cardiac activity was also collected at 7, 10, and 13 months followin a 20-min long battery of emotion-eliciting stimuli. Significant developmental increases were observed in heart period but not in the measure of cardiac vagal tone. Stress-related decreases in cardiac vagal tone and increases in heart rate were observed after the emotion-eliciting stimuli ended. Individual differences in measures of heart period and cardiac vagal tone were stable over 2- and 3-month periods.

Effects of Aerosol Ipratropium Bromide on Cardiac Vagal Tone

Thirty-one adult asthmatic subjects, aged 18 to 40 years, were administered both ipratropium bromide and placebo, in two sessions, held at least 2 days apart, in balanced order. Pulmonary function, heart period (milliseconds between heart beats), and respiratory sinus arrhythmia (a measure of cardiac vagal tone) were assessed before drug administration and 45 min thereafter. Ipratropium bromide had no significant effect on cardiac vagal tone, while it did produce improvement in pulmonary function.

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.

Accuracy of assessment of cardiac vagal tone by heart rate variability in normal subjects

The correlations of 11 indexes of heart rate variability were examined with pharmacologically determined cardiac vagal tone in 15 normal subjects at supine rest. After sympathetic influences by intravenous propranolol were eliminated, RR interval variability was measured for 10 minutes under controlled respiration (0.25 Hz), and cardiac vagal tone was determined as the decrease in mean RR interval following complete vagal blockade with atropine. Time domain indexes (standard deviation, coefficient of variance and mean successive difference) correlated strongly with vagal tone (r = 0.87, 0.81 and 0.92, respectively; p < 0.001 for all). The same was true for frequency domain indexes for the high-frequency (0.25 Hz) component calculated both by autoregressive spectrum analysis (square root of power and coefficient of component variance) and by fast Fourier transform (mean amplitude) (r = 0.91, 0.85 and 0.86, respectively; p < 0.0001 for all). However, frequency domain indexes for the low-frequency spectral component (0.03 to 0.15 Hz) correlated less strongly (r = 0.69, 0.55 and 0.70, respectively), and the fraction of power [power/(total power > 0.03 Hz)] of both components showed no correlation. Principal component analysis showed that the first 6 indexes with strong correlations contained solely the first principal component closely related to vagal tone, whereas the remaining 5 indexes also contained the second component unrelated to vagal tone. These results indicate that most of the time and frequency domain analyses in use provides an accurate and common measure of cardiac vagal tone at rest.

Cardiopulmonary Adjustments During Operant Heart Rate Control

Twenty-three healthy men and women participated in a 5-session experiment in which they attempted to increase and decrease their heart rate with the assistance of visual analogue biofeedback. As a group subjects did successfully raise and lower heart rate from resting baseline. These changes in heart rate were closely paralleled by changes in V, a measure of cardiac vagal tone. Heart rate slowing was associated with increases in V, and heart rate speeding was associated with decreases in V. Respiration rate and amplitude did not differ significantly between heart rate slowing and speeding trials, and covariance analysis indicated that respiratory changes did not account for the heart rate or V effects. The weighted coherence between respiration and heart rate showed that cardiopulmonary coupling increased during heart rate slowing and decreased during heart rate speeding. Individual differences in cardiac vagal tone and cardiopulmonary coupling were unrelated to heart rate speeding and slowing performance.

The Relation between Neonatal Heart Period Patterns and Developmental Outcome

Developmental psychophysiologists have long been interested in a means for evaluating infants at risk for cognitive disabilities. The current research addressed the utility of a noninvasive measure of cardiac vagal tone in predicting developmental outcome. At 40 weeks conceptional age, 3 min of resting EKG were recorded from 80 infants. Four groups of infants were evaluated: prematures who had no medical complications in the postnatal period; prematures who experienced respiratory distress syndrome during the postnatal period; term infants who experienced birth asphyxia during labor and/or postdelivery; and healthy term infants. The mental scale of the Bayley Scales of Mental Development was administered at 8 and 12 months conceptional age. Heart period data were analyzed to derive mean heart period, heart period variability, and estimates of vagal tone for each subject. Analyses of the relationship between the heart period variables and 8- and 12-month outcome (i.e., Bayley Scales) indicated that infants with high vagal tone at 40 weeks conceptional age always had positive developmental outcome at both eight and 12 months of age. Infants with low vagal tone had varied outcomes. Measures of medical complications and other measures of heart period variability were not related to developmental outcome. The results suggest that measurement of cardiac vagal tone may provide an important means for assessing risk in birth stressed populations.