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

Summary Motivation: 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. Objective: 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. Methods: 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. Results and Conclusion: 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… 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.

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Assessment of parasympathetic control of heart rate by a noninvasive method

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1984.246.6.h838 ◽

1984 ◽

Vol 246 (6) ◽

pp. H838-H842 ◽

Cited By ~ 25

Author(s):

F. M. Fouad ◽

R. C. Tarazi ◽

C. M. Ferrario ◽

S. Fighaly ◽

C. Alicandri

Keyword(s):

Heart Rate ◽

Respiratory Sinus Arrhythmia ◽

Separate Group ◽

Noninvasive Method ◽

Sinus Arrhythmia ◽

Beta Adrenergic ◽

Normal Volunteers ◽

Vagal Control ◽

Parasympathetic Control ◽

The Relationship

The degree of parasympathetic control of heart rate was assessed by the abolition of respiratory sinus arrhythmia with atropine. Peak-to-peak variations in heart periods (VHP) before atropine injection correlated significantly (r = 0.90, P less than 0.001) with parasympathetic control, indicating that VHP alone may be used as a noninvasive indicator of the parasympathetic control of heart rate. Pharmacologic blockade of beta-adrenergic supply in a separate group of normal volunteers did not alter the relationship between VHP and parasympathetic control, indicating that the condition of the experiment (complete rest in a quiet atmosphere) allows the use of VHP alone without pharmacologic interventions to characterize the vagal control of heart rate in humans.

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Associations between Acoustic Features of Maternal Speech and Infants' Emotion Regulation following a Social Stressor

10.1101/2021.07.02.450379 ◽

2021 ◽

Author(s):

Jacek Kolacz ◽

Elizabeth B daSilva ◽

Gregory F Lewis ◽

Bennett I Bertenthal ◽

Stephen W Porges

Keyword(s):

Heart Rate ◽

Social Engagement ◽

Vagal Tone ◽

Fast Fourier Transformation ◽

Acoustic Features ◽

Sinus Arrhythmia ◽

Cardiac Vagal Tone ◽

Gaze Aversion ◽

Maternal Speech ◽

Electrocardiogram Ecg

Caregiver voices may provide cues to mobilize or calm infants. This study examined whether maternal prosody predicted changes in infants' biobehavioral state during the Still Face, a stressor in which the mother withdraws and reinstates social engagement. Ninety-four dyads participated in the study (infant age 4-8 months). Infants' heart rate and respiratory sinus arrhythmia (measuring cardiac vagal tone) were derived from an electrocardiogram (ECG). Infants' behavioral distress was measured by negative vocalizations, facial expressions, and gaze aversion. Mothers' vocalizations were measured with spectral analysis and spectro-temporal modulation using a two-dimensional fast Fourier transformation of the audio spectrogram. High values on the maternal prosody composite were associated with decreases in infants' heart rate (β=-.26, 95% CI: [-.46, -.05]) and behavioral distress (β=- .20, 95% CI: [-.38, -.02]), and increases in cardiac vagal tone in infants whose vagal tone was low during the stressor (1 SD below mean β=.39, 95% CI: [.06, .73]). High infant heart rate predicted increases in the maternal prosody composite (β=.18, 95% CI: [.03, .33]). These results suggest specific vocal acoustic features of speech that are relevant for regulating infants' biobehavioral state and demonstrate mother-infant bi-directional dynamics.

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

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1990.258.3.h896 ◽

1990 ◽

Vol 258 (3) ◽

pp. H896-H902 ◽

Cited By ~ 13

Author(s):

G. E. Billman ◽

J. P. Dujardin

Keyword(s):

Heart Rate ◽

Time Series ◽

Time Series Analysis ◽

Rate Control ◽

Vagal Tone ◽

Heart Rate Control ◽

Dynamic Changes ◽

Sinus Arrhythmia ◽

Cardiac Vagal Tone ◽

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.

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Does respiratory sinus arrhythmia occur in fishes?

Biology Letters ◽

10.1098/rsbl.2005.0365 ◽

2005 ◽

Vol 1 (4) ◽

pp. 484-487 ◽

Cited By ~ 15

Author(s):

Hamish A Campbell ◽

Edwin W Taylor ◽

Stuart Egginton

Keyword(s):

Heart Rate ◽

Respiratory Sinus Arrhythmia ◽

Selection Pressure ◽

Vagal Activity ◽

Sinus Arrhythmia ◽

Antarctic Species ◽

Power Spectral ◽

Spectral Statistics ◽

Respiratory Modulation ◽

Environmental Temperatures

The hypothesis that respiratory modulation of heart rate variability (HRV) or respiratory sinus arrhythmia (RSA) is restricted to mammals was tested on four Antarctic and four sub-Antarctic species of fish, that shared close genotypic or ecotypic similarities but, due to their different environmental temperatures, faced vastly different selection pressures related to oxygen supply. The intrinsic heart rate ( f H ) for all the fish species studied was ∼25% greater than respiration rate ( f V ), but vagal activity successively delayed heart beats, producing a resting f H that was synchronized with f V in a progressive manner. Power spectral statistics showed that these episodes of relative bradycardia occurred in a cyclical manner every 2–4 heart beats in temperate species but at >4 heart beats in Antarctic species, indicating a more relaxed selection pressure for cardio-respiratory coupling. This evidence that vagally mediated control of f H operates around the ventilatory cycle in fish demonstrates that influences similar to those controlling RSA in mammals operate in non-mammalian vertebrates.

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Effects of hypercapnia and hypoxemia on respiratory sinus arrhythmia in conscious humans during spontaneous respiration

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00817.2006 ◽

2007 ◽

Vol 292 (5) ◽

pp. H2397-H2407 ◽

Cited By ~ 28

Author(s):

Y. C. Tzeng ◽

P. D. Larsen ◽

D. C. Galletly

Keyword(s):

Tidal Volume ◽

Respiratory Sinus Arrhythmia ◽

Amplitude Ratio ◽

Low Frequency ◽

Vagal Tone ◽

Mean Amplitude ◽

Spontaneous Respiration ◽

Vagal Activity ◽

Sinus Arrhythmia ◽

Amplitude Increase

Normally, at rest, the amplitude of respiratory sinus arrhythmia (RSA) appears to correlate with cardiac vagal tone. However, recent studies showed that, under stress, RSA dissociates from vagal tone, indicating that separate mechanisms might regulate phasic and tonic vagal activity. This dissociation has been linked to the hypothesis that RSA improves pulmonary gas exchange through preferential distribution of heartbeats in inspiration. We examined the effects of hypercapnia and mild hypoxemia on RSA-vagal dissociation in relation to heartbeat distribution throughout the respiratory cycle in 12 volunteers. We found that hypercapnia, but not hypoxemia, was associated with significant increases in heart rate (HR), tidal volume, and RSA amplitude. The RSA amplitude increase remained statistically significant after adjustment for respiratory rate, tidal volume, and HR. Moreover, the RSA amplitude increase was associated with a paradoxical rise in HR and decrease in low-frequency-to-high-frequency mean amplitude ratio derived from spectral analysis, which is consistent with RSA-vagal dissociation. Although hypercapnia was associated with a significant increase in the percentage of heartbeats during inspiration, this association was largely secondary to increases in the inspiratory period-to-respiratory period ratio, rather than RSA amplitude. Additional model analyses of RSA were consistent with the experimental data. Heartbeat distribution did not change during hypoxemia. These results support the concept of RSA-vagal dissociation during hypercapnia; however, the putative role of RSA in optimizing pulmonary perfusion matching requires further experimental validation.

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Cardiac Vagal Tone and Stress

Oxford Research Encyclopedia of Neuroscience ◽

10.1093/acrefore/9780190264086.013.268 ◽

2021 ◽

Author(s):

Kevin T. Larkin ◽

Alaina G. Tiani ◽

Leah A. Brown

Keyword(s):

Heart Rate ◽

Psychiatric Disorders ◽

Empirical Work ◽

Vagal Tone ◽

Vagal Nerve ◽

Vagal Activity ◽

Polyvagal Theory ◽

Cardiac Vagal Tone ◽

Parasympathetic Nerve ◽

Cortical Regions

Based on its distinctive innervation between the brain and body, the vagal nerve has long been considered to play an important role in explaining how exposure to stress leads to numerous psychiatric disorders and cardiac diseases. In contrast to activation of the sympathetic nervous system during exposures to stress, the vagal nerve is responsible for parasympathetic regulation of visceral activity including cardiac functioning that often but not always co-occurs during periods of stress. Although methods exist to measure vagal nerve influences on the heart directly, most of the literature on both human and animal participants’ responses to stress employs the measurement of heart rate variability (HRV). HRV, the tendency for the heart rate to increase and decrease in adaptation to the changing physiological and external environment, can be easily detected using surface electrodes; several HRV parameters have been shown to be valid indicators of parasympathetic nerve activity. Theories of the evolutionary heritage of the vagal nerve, like Porges’ polyvagal theory and the subsequent neurovisceral integration perspective of Thayer and colleagues that traces the autonomic regulation of the heart into higher cortical regions, have served as important conceptual works to guide empirical work examining the effects of stress on both tonic and phasic vagal activity. A number of methodological approaches have been employed to evaluate whether exposure to stress affects vagal tone, including use of animal models, case-control samples of humans exposed to stressful living situations, and samples of humans diagnosed with a range of psychiatric disorders. Findings from studies comprising this literature support a relation between exposure to stress and reduced cardiac vagal tone. Both humans and animals typically exhibit reductions in daily HRV when exposed to a range of stressful situations or contexts. The relation between stress and phasic alterations in vagal functioning, the magnitude of the acute change in HRV in response to an acute stressor, is more complicated, likely involving significant moderating variables that have yet to be elucidated. In sum, considerable evidence supports an important neuroregulatory role of the vagal nerve in modulating the body’s response to environmental stress and potentially serving as an avenue for understanding how exposure to stress increases risk for psychiatric disorders as well as cardiovascular disease.

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Respiratory Sinus Arrhythmia in Blood Phobic Subjects

Perceptual and Motor Skills ◽

10.2466/pms.1997.84.2.505 ◽

1997 ◽

Vol 84 (2) ◽

pp. 505-506 ◽

Cited By ~ 8

Author(s):

Alessandro Angrilli ◽

Michela Sarlo ◽

Daniela Palomba ◽

Micaela Schincaglia ◽

Luciano Stegagno

Keyword(s):

Heart Rate ◽

Respiratory Sinus Arrhythmia ◽

Vagal Activity ◽

Sinus Arrhythmia ◽

Control Subjects ◽

Paced Respiration ◽

Autonomic Index ◽

Vagal Influence

12 blood-phobic subjects, selected according to the Feat Survey Schedule and the Mutilation Questionnaire, and 50 control subjects performed a paced respiration task during which heart rate and respiration were recorded. Respiratory Sinus Arrhythmia (RSA) was analyzed as an autonomic index of vagal influence on the heart. Analysis showed a larger RSA in the blood-phobic group than the controls and points to a difference in vagal activity at rest between the groups.

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Autonomic response to coronary occlusion in animals susceptible to ventricular fibrillation

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1989.257.6.h1886 ◽

1989 ◽

Vol 257 (6) ◽

pp. H1886-H1894 ◽

Cited By ~ 18

Author(s):

M. N. Collins ◽

G. E. Billman

Keyword(s):

Heart Rate ◽

Ventricular Fibrillation ◽

Coronary Occlusion ◽

Rate Increase ◽

Vagal Tone ◽

Autonomic Response ◽

Acute Ischemia ◽

Heart Rate Increase ◽

Sinus Arrhythmia ◽

Cardiac Vagal Tone

Disturbances in autonomic control during myocardial ischemia may contribute significantly to the development of malignant cardiac arrhythmias. Therefore acute ischemia was induced in 29 mongrel dogs with healed myocardial infarctions during an exercise test. Seventeen animals developed ventricular fibrillation (susceptible, S), whereas 12 dogs did not (resistant, R). Before the exercise plus ischemia test a coronary occlusion was made at rest. The amplitude of respiratory sinus arrhythmia (0.24- to 1.04-Hz component of R-R interval fluctuation) was used as an index of cardiac vagal tone. Acute ischemia elicited a significantly larger heart rate increase in susceptible animals (S: control 115.6 +/- 0.8, occlusion 176.4 +/- 8.2 beats/min vs. R: control 114.6 +/- 8.9, occlusion 145.7 +/- 7.5 beats/min). Accompanying the heart rate increase were significantly greater reductions in the cardiac vagal tone index in the susceptible animals. (S: control 6.4 +/- 0.3, occlusion 2.2 +/- 0.6 ln ms2 vs. R: control 6.6 +/- 0.4, occlusion 5.1 +/- 0.5 ln ms2). beta-Adrenergic receptor blockade reduced the heart rate increases but exacerbated the reductions in the cardiac vagal tone index. These data suggest that coronary artery occlusion elicits a significantly greater increase in sympathetic activity coupled with a greater reduction in parasympathetic activity in animals subsequently shown to be susceptible to ventricular fibrillation.

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