Effects of digoxin and enalapril on heart period variability and response to head-up tilt in normal subjects

We exploit time reversibility analysis, checking the invariance of statistical features of a series after time reversal, to detect temporal asymmetries of short-term heart period variability series. Reversibility indexes were extracted from 22 healthy fetuses between 16th to 40th wk of gestation and from 17 healthy humans (aged 21 to 54, median = 28) during graded head-up tilt with table inclination angles randomly selected inside the set {15, 30, 45, 60, 75, 90}. Irreversibility analysis showed that nonlinear dynamics observed in short-term heart period variability are mostly due to asymmetric patterns characterized by bradycardic runs shorter than tachycardic ones. These temporal asymmetries were 1) more likely over short temporal scales than over longer, dominant ones; 2) more frequent during the late period of pregnancy (from 25th to 40th week of gestation); 3) significantly present in healthy humans at rest in supine position; 4) more numerous during 75 and 90° head-up tilt. Results suggest that asymmetric patterns observable in short-term heart period variability might be the result of a fully developed autonomic regulation and that an important shift of the sympathovagal balance toward sympathetic predominance (and vagal withdrawal) can increase their presence.

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Short-term variability of blood pressure and heart rate in Guillain-Barreá syndrome without respiratory failure

Clinical Science ◽

10.1042/cs0960613 ◽

1999 ◽

Vol 96 (6) ◽

pp. 613-621 ◽

Cited By ~ 1

Author(s):

Djillali ANNANE ◽

Véronique BAUDRIE ◽

Anne-Sophie BLANC ◽

Dominique LAUDE ◽

Jean-Claude RAPHAËL ◽

...

Keyword(s):

Blood Pressure ◽

Heart Rate ◽

Respiratory Failure ◽

Plasma Noradrenaline ◽

Heart Period ◽

Short Term ◽

Heart Period Variability ◽

Period Variability ◽

Head Up Tilt ◽

Short Term Variability

The effect of Guillain-Barré syndrome (GBS) on the short-term variability of blood pressure and heart rate was evaluated in six patients presenting with a moderate form of the syndrome, i.e. unable to stand up unaided and without respiratory failure, at the height of the disease and during recovery. The patients were compared with six age-matched healthy volunteers. During the acute phase of the syndrome, GBS patients exhibited a significant heart rate elevation (+26 beats/min compared with healthy subjects), but the acceleratory response to atropine, or to 60 ° head-up tilt, was maintained. Resting plasma noradrenaline levels were high in acute GBS, but the secretory response to tilt was preserved. Desensitization to noradrenaline was observed in acute GBS with a reduced pressor action of this α-adrenoceptor agonist. Blood pressure levels were normal and head-up tilt did not induce orthostatic hypotension in this moderate form of GBS. Power spectral analysis demonstrated marked alterations in cardiovascular variability. The overall heart period variability was markedly reduced with the reduction predominantly in the high-frequency (respiratory) range (-73%). The low-frequency component of heart period variability was also reduced (-54%). This cardiovascular profile of moderate GBS at the height of the disease could result from a demyelination of the reflex loop controlling respiratory oscillations in heart rate and from a desensitization of the arterial tree to an elevated plasma noradrenaline. Sympathetic nervous activation may contribute to the high resting heart rate in acute GBS.

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Progressive decrease of heart period variability entropy-based complexity during graded head-up tilt

Journal of Applied Physiology ◽

10.1152/japplphysiol.00293.2007 ◽

2007 ◽

Vol 103 (4) ◽

pp. 1143-1149 ◽

Cited By ~ 147

Author(s):

Alberto Porta ◽

Tomaso Gnecchi-Ruscone ◽

Eleonora Tobaldini ◽

Stefano Guzzetti ◽

Raffaello Furlan ◽

...

Keyword(s):

Complexity Analysis ◽

Conditional Entropy ◽

Approximate Entropy ◽

Tilt Test ◽

Sympathovagal Balance ◽

Heart Period ◽

Progressive Decrease ◽

Heart Period Variability ◽

Period Variability ◽

Head Up Tilt

Complexity (or its opposite, regularity) of heart period variability has been related to age and disease but never linked to a progressive shift of the sympathovagal balance. We compare several well established estimates of complexity of heart period variability based on entropy rates [i.e., approximate entropy (ApEn), sample entropy (SampEn), and correct conditional entropy (CCE)] during an experimental protocol known to produce a gradual shift of the sympathovagal balance toward sympathetic activation and vagal withdrawal (i.e., the graded head-up tilt test). Complexity analysis was carried out in 17 healthy subjects over short heart period variability series (∼250 cardiac beats) derived from ECG recordings during head-up tilt with table inclination randomly chosen inside the set {0, 15, 30, 45, 60, 75, 90}. We found that 1) ApEn does not change significantly during the protocol; 2) all indices measuring complexity based on entropy rates, including ad hoc corrections of the bias arising from their evaluation over short data sequences (i.e., corrected ApEn, SampEn, CCE), evidence a progressive decrease of complexity as a function of the tilt table inclination, thus indicating that complexity is under control of the autonomic nervous system; 3) corrected ApEn, SampEn, and CCE provide global indices that can be helpful to monitor sympathovagal balance.

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Spectral characteristics of heart period variability during cold face stress and shock avoidance in normal subjects

Clinical Autonomic Research ◽

10.1007/bf02281901 ◽

1996 ◽

Vol 6 (3) ◽

pp. 147-152 ◽

Cited By ~ 21

Author(s):

B. H. Friedman ◽

J. F. Thayer ◽

R. A. Tyrrell

Keyword(s):

Spectral Characteristics ◽

Normal Subjects ◽

Shock Avoidance ◽

Heart Period ◽

Heart Period Variability ◽

Period Variability ◽

Cold Face

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Effects of Fear Induction on Heart Period Variability

Journal of Psychophysiology ◽

10.1027//0269-8803.13.1.18 ◽

1999 ◽

Vol 13 (1) ◽

pp. 18-26 ◽

Cited By ~ 3

Author(s):

Rudolf Stark ◽

Alfons Hamm ◽

Anne Schienle ◽

Bertram Walter ◽

Dieter Vaitl

Keyword(s):

Blood Pressure ◽

Trait Anxiety ◽

State Anxiety ◽

Self Report ◽

Emotional States ◽

Heart Period ◽

Experimental Conditions ◽

Heart Period Variability ◽

Physiological Variables ◽

Period Variability

Abstract The present study investigated the influence of contextual fear in comparison to relaxation on heart period variability (HPV), and analyzed differences in HPV between low and high anxious, nonclinical subjects. Fifty-three women participated in the study. Each subject underwent four experimental conditions (control, fear, relaxation, and a combined fear-relaxation condition), lasting 10 min each. Fear was provoked by an unpredictable aversive human scream. Relaxation should be induced with the aid of verbal instructions. To control for respiratory effects on HPV, breathing was paced at 0.2 Hz using an indirect light source. Besides physiological measures (HPV measures, ECG, respiration, forearm EMG, blood pressure), emotional states (pleasure, arousal, dominance, state anxiety) were assessed by subjects' self-reports. Since relaxation instructions did not have any effect neither on the subjective nor on the physiological variables, the present paper focuses on the comparison of the control and the fear condition. The scream reliably induced changes in both physiological and self-report measures. During the fear condition, subjects reported more arousal and state anxiety as well as less pleasure and dominance. Heart period decreased, while EMG and diastolic blood pressure showed a tendency to increase. HPV remained largely unaltered with the exception of the LF component, which slightly decreased under fear induction. Replicating previous findings, trait anxiety was negatively associated with HPV, but there were no treatment-specific differences between subjects with low and high trait anxiety.

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