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Julian F. R. Paton - One of the best experts on this subject based on the ideXlab platform.

  • enhancing Respiratory Sinus Arrhythmia increases cardiac output in rats with left ventricular dysfunction
    The Journal of Physiology, 2020
    Co-Authors: E L Ocallaghan, Renata Maria Lataro, Eva V. L. Roloff, Ashok Chauhan, Helio Cesar Salgado, Edward Duncan, Alain Nogaret, Julian F. R. Paton
    Abstract:

    KEY POINTS: Respiratory Sinus Arrhythmia is physiological pacing of the heart that disappears in cardiovascular disease and is associated with poor cardiac prognosis. In heart failure, cardiac pacing has little, if any, variation in rate at rest. We proposed that reinstatement of Respiratory Sinus Arrhythmia would improve cardiac function in rats with heart failure. Heart failure rats were paced daily for 2 weeks with either Respiratory Sinus Arrhythmia or paced monotonically at a matched heart rate; cardiac function was measured using non-invasive echocardiography. Cardiac output and stroke volume were increased in rats paced with Respiratory Sinus Arrhythmia compared to monotonic pacing, via improvement in systolic function that persisted beyond the pacing treatment period. We propose that Respiratory Sinus Arrhythmia pacing reverse-remodels the heart in heart failure and is worth considering as a new form of cardiac pacemaking. ABSTRACT: Natural pacing of the heart results in heart rate variability, an indicator of good health and cardiac function. A contributor to heart rate variability is Respiratory Sinus Arrhythmia or RSA - an intrinsic Respiratory modulated pacing of heart rate. The loss of RSA is associated with poor cardiac prognosis and sudden cardiac death. We tested if reinstatement of Respiratory-modulated heart rate (RMH) would improve cardiac performance in heart failure. Heart failure was induced in Wistar rats by ligation of the left anterior descending coronary artery. Rats were unpaced, monotonically paced and RMH paced; the latter had the same average heart rate as the monotonically paced animals. Cardiac function was assessed non-invasively using echocardiography before and after 2 weeks of daily pacing at a time when pacing was turned off. RMH increased cardiac output by 20 ± 8% compared to monotonic pacing (-3 ± 5%; P < 0.05). This improvement in cardiac output was associated with an increase in stroke volume compared to monotonic pacing (P = 0.03) and improvement in circumferential strain (P = 0.02). Improvements in ejection fraction (P = 0.08) and surrogate measures of left ventricle compliance did not reach significance. Increases in contractility (P < 0.05) and coronary blood flow (P < 0.05) were seen in vitro during variable pacing to mimic RMH. Thus, in rats with left ventricular dysfunction, chronic RMH pacing improved cardiac function through improvements in systolic function. As these improvements were made with pacing switched off, we propose the novel idea that RMH pacing causes reverse-remodelling.

  • Enhancing Respiratory Sinus Arrhythmia increases cardiac output in rats with left ventricular dysfunction.
    The Journal of Physiology, 2019
    Co-Authors: El O'callaghan, Renata Maria Lataro, Eva V. L. Roloff, Ashok Chauhan, Helio Cesar Salgado, Edward Duncan, Alain Nogaret, Julian F. R. Paton
    Abstract:

    KEY POINTS: Respiratory Sinus Arrhythmia is physiological pacing of the heart that disappears in cardiovascular disease and is associated with poor cardiac prognosis. In heart failure, cardiac pacing has little, if any, variation in rate at rest. We proposed that reinstatement of Respiratory Sinus Arrhythmia would improve cardiac function in rats with heart failure. Heart failure rats were paced daily for 2 weeks with either Respiratory Sinus Arrhythmia or paced monotonically at a matched heart rate; cardiac function was measured using non-invasive echocardiography. Cardiac output and stroke volume were increased in rats paced with Respiratory Sinus Arrhythmia compared to monotonic pacing, via improvement in systolic function that persisted beyond the pacing treatment period. We propose that Respiratory Sinus Arrhythmia pacing reverse-remodels the heart in heart failure and is worth considering as a new form of cardiac pacemaking. ABSTRACT: Natural pacing of the heart results in heart rate variability, an indicator of good health and cardiac function. A contributor to heart rate variability is Respiratory Sinus Arrhythmia or RSA - an intrinsic Respiratory modulated pacing of heart rate. The loss of RSA is associated with poor cardiac prognosis and sudden cardiac death. We tested if reinstatement of Respiratory-modulated heart rate (RMH) would improve cardiac performance in heart failure. Heart failure was induced in Wistar rats by ligation of the left anterior descending coronary artery. Rats were unpaced, monotonically paced and RMH paced; the latter had the same average heart rate as the monotonically paced animals. Cardiac function was assessed non-invasively using echocardiography before and after 2 weeks of daily pacing at a time when pacing was turned off. RMH increased cardiac output by 20 ± 8% compared to monotonic pacing (-3 ± 5%; P 

  • modulation of Respiratory Sinus Arrhythmia in rats with central pattern generator hardware
    Journal of Neuroscience Methods, 2013
    Co-Authors: Alain Nogaret, Le Zhao, Davi J A Moraes, Julian F. R. Paton
    Abstract:

    Abstract We report on the modulation of Respiratory Sinus Arrhythmia in rats with central pattern generator (CPG) hardware made of silicon neurons. The neurons are made to compete through mutually inhibitory synapses to provide timed electrical oscillations that stimulate the peripheral end of vagus nerve at specific points of the Respiratory cycle: the inspiratory phase (φ1), the early expiratory phase (φ2) and the late expiratory phase (φ3). In this way the CPG hardware mimics the neuron populations in the brainstem which through connections with cardiac vagal motoneurones control Respiratory Sinus Arrhythmia (RSA). Here, we time the output of the CPG hardware from the phrenic nerve activity recorded from rats while monitoring heart rate changes evoked by vagal nerve stimulation (derived from ECG) controlled by the CPG. This neuroelectric stimulation has the effect of reducing the heart rate and increasing the arterial pressure. The artificially induced RSA strongly depends on the timing of pulses within the breathing cycle. It is strongest when the vagus nerve is stimulated during the inspiratory phase (φ1) or the early expiratory phase (φ2) in which case the heart rate slows by 50% of the normal rate. Heart rate modulation is less when the same exact stimulus is applied during the late expiratory phase (φ3). These trials show that neurostimulation by CPG hardware can augment Respiratory Sinus Arrhythmia. The CPG hardware technology opens a new line of therapeutic possibilities for prosthetic devices that restore RSA in patients where Respiratory-cardiac coupling has been lost.

  • A theoretical study of the physiological significance of Respiratory Sinus Arrhythmia
    The FASEB Journal, 2012
    Co-Authors: Sophie S. Shamailov, Julian F. R. Paton
    Abstract:

    Respiratory Sinus Arrhythmia (RSA) is a phenomenon whereby the heart rate increases during inspiration and decreases during expiration. We used mathematical models to test two hypotheses for the ph...

Paul Grossman - One of the best experts on this subject based on the ideXlab platform.

  • prediction of tonic parasympathetic cardiac control using Respiratory Sinus Arrhythmia the need for Respiratory control
    Psychophysiology, 1991
    Co-Authors: Paul Grossman, John M Karemaker, Wouter Wieling
    Abstract:

    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.

  • a comparison of three quantification methods for estimation of Respiratory Sinus Arrhythmia
    Psychophysiology, 1990
    Co-Authors: Paul Grossman, J H G M Van Beek, Cornelis J E Wientjes
    Abstract:

    : The empirical literature has shown that Respiratory Sinus Arrhythmia is a sensitive noninvasive index of parasympathetic cardiac control. Nevertheless there has been no general agreement among investigators as to the most preferable quantification technique for assessing Respiratory Sinus Arrhythmia, although there has been much speculation that specific estimation techniques are more or less reflective of vagal processes and could be more or less contaminated by other influences upon heart period variability unrelated to respiration. This study compared three quantification procedures for estimating Respiratory Sinus Arrhythmia (RSA): (1) a spectral analytic technique, (2) a complex detrending approach removing periodic and aperiodic cardiac variations unrelated to respiration, and (3) a time-domain, peak-valley procedure employing inspiratory and expiratory periods as windows for determining range of cardiac-interval fluctuations associated with Respiratory phase. Measures derived from these techniques were intra- and interindividually compared using three different samples of male subjects, including students, adult normotensives, and adult hypertensives. All interindividual correlations between measures yielded coefficients above .92 and the mean within-subject correlation across 42 individuals was .96, thus indicating a marked degree of comparability between measures. Additionally, given that much evidence indicates lawful within-individual relations between RSA amplitude and Respiratory parameters, we employed Respiratory period as an external criterion and compared intraindividual correlations between this variable and (2) and (3); results showed that (3) was significantly more highly associated with respiration than was (2), although the mean r's for the two measures did not diverge greatly (.91 vs. .84). Finally, inspection of the data and further regression analyses did not suggest that any of the RSA estimates were differentially contaminated by other components of cardiac variability. Our findings suggest that the three techniques are almost equivalent as indices of cardiac vagal tone and would appear to ease concerns about the inferiority of any of the procedures. Choice of a quantification procedure should therefore be tailored to the specific empirical needs of an investigation. The advantages and disadvantages of each method are discussed.

  • paced Respiratory Sinus Arrhythmia as an index of cardiac parasympathetic tone during varying behavioral tasks
    Psychophysiology, 1990
    Co-Authors: Paul Grossman, Gerhard Stemmler, Erik Meinhardt
    Abstract:

    : This study addresses a number of unresolved issues regarding the employment of Respiratory Sinus Arrhythmia as an index of tonic parasympathetic cardiac control in psychophysiological investigations. These questions include the following: (1) Does Respiratory Sinus Arrhythmia reflect cardiac vagal tone under conditions in which alterations in parasympathetic control are expected to be mild to moderate? (2) Are variations in human Respiratory Sinus Arrhythmia that occur in response to varying behavioral demands independent of beta-adrenergic effects on the heart? (3) To what extent do typical experimental tasks apparently affect tonic cardiac vagal control? Twelve healthy male subjects were administered a joint alpha- and beta-adrenoreceptor pharmacological blocker on one day and a placebo on another (balanced across subjects). On both days, Respiratory Sinus Arrhythmia and heart period were monitored during a number of different experimental tasks while subjects continuously paced their respiration. Results indicated that Respiratory Sinus Arrhythmia, under controlled Respiratory conditions, is uninfluenced by variations in sympathetic activity, and provides a reasonably sensitive index of cardiac vagal tone, even when alterations in parasympathetic tone are not large. Furthermore, our findings suggest that cardiac vagal tone is responsive to varying behavioral demands and may interact in different ways with beta-adrenergic mechanisms.

Stephen W Porges - One of the best experts on this subject based on the ideXlab platform.

  • Respiratory Sinus Arrhythmia and ambient temperature at 5 months
    Infant Behavior & Development, 1997
    Co-Authors: Todd C. Riniolo, Olga V. Bazhenova, Stephen W Porges
    Abstract:

    Infants were tested in a clinical environment that did not control ambient temperature and assigned, post-hoc, into 80°F groups. Respiratory Sinus Arrhythmia was suppressed in response to the elevated temperature. The findings suggest that temperature should be controlled during psychophysiological research with infants.

  • data dependent filter characteristics of peak valley Respiratory Sinus Arrhythmia estimation a cautionary note
    Psychophysiology, 1993
    Co-Authors: Evan A Byrne, Stephen W Porges
    Abstract:

    Filter characteristics of the peak-valley Respiratory Sinus Arrhythmia estimation method are described. To identify filter characteristics of this method, models were generated that combined signals of different frequencies with trends of varying slopes. These models simulate the influence of trend and changing Respiratory frequency on the accuracy of peak-valley estimates. The transfer function of the peak-valley method, unlike that of other time domain filters, is not solely dependent upon signal frequency. Two factors interact to determine the relative accuracy of the peak-valley method: (a) slope of the signal component and (b) slope of the underlying trend. Combinations of these factors may result in significant distortion to the input signal. The direction of error is a function of the direction of the trend (i.e., overestimation with deceleration and underestimation with acceleration). In many situations when Respiratory Sinus Arrhythmia amplitude is low in special populations (e.g., cardiovascular disorders, high-risk infants, or human fetuses) or under conditions that greatly reduce Respiratory Sinus Arrhythmia amplitude (e.g., exercise, drugs, pharmacological manipulations), use of the peak-valley method may result in significant measurement error. The use of this method to evaluate Respiratory Sinus Arrhythmia over short epochs (i.e., less than 2 min) or to quantify changes in Respiratory Sinus Arrhythmia due to discrete stimulation (e.g., breath by breath) may result in inconsistent measurement error. Recommendations are made for detrending heart rate data prior to application of the peak-valley method.

  • Data‐dependent filter characteristics of peak‐valley Respiratory Sinus Arrhythmia estimation: A cautionary note
    Psychophysiology, 1993
    Co-Authors: Evan A Byrne, Stephen W Porges
    Abstract:

    : Filter characteristics of the peak-valley Respiratory Sinus Arrhythmia estimation method are described. To identify filter characteristics of this method, models were generated that combined signals of different frequencies with trends of varying slopes. These models simulate the influence of trend and changing Respiratory frequency on the accuracy of peak-valley estimates. The transfer function of the peak-valley method, unlike that of other time domain filters, is not solely dependent upon signal frequency. Two factors interact to determine the relative accuracy of the peak-valley method: (a) slope of the signal component and (b) slope of the underlying trend. Combinations of these factors may result in significant distortion to the input signal. The direction of error is a function of the direction of the trend (i.e., overestimation with deceleration and underestimation with acceleration). In many situations when Respiratory Sinus Arrhythmia amplitude is low in special populations (e.g., cardiovascular disorders, high-risk infants, or human fetuses) or under conditions that greatly reduce Respiratory Sinus Arrhythmia amplitude (e.g., exercise, drugs, pharmacological manipulations), use of the peak-valley method may result in significant measurement error. The use of this method to evaluate Respiratory Sinus Arrhythmia over short epochs (i.e., less than 2 min) or to quantify changes in Respiratory Sinus Arrhythmia due to discrete stimulation (e.g., breath by breath) may result in inconsistent measurement error. Recommendations are made for detrending heart rate data prior to application of the peak-valley method.

Manuel Paiva - One of the best experts on this subject based on the ideXlab platform.

Pierrefrancois Migeotte - One of the best experts on this subject based on the ideXlab platform.