Autonomic Regulation Of Circulation Research Articles

The Autonomic Regulation of Circulation and Adverse Events in Hypertensive Patients during Follow-Up Study.

Purpose Comprehensive study of autonomic regulation assessed during follow-up could provide new detailed information about the risks stratification for hypertensive patients. Therefore, we investigated the associations of these indices with death, stroke, and revascularization during the follow-up observation of 55 patients. Methods All patients were with target organ damage, and 27 of them had associated clinical conditions (ACC). Mean age of patients with and without ACC was 62.6 ± 4.2 and 51.9 ± 9.9 (mean ± SD) years, respectively. Follow-up was from 66 to 95 months. At entry, autonomic regulation was assessed by the tilt test, Valsalva maneuver, hand-grip test, and cold-stress vasoconstriction. Hemodynamic parameters were measured by continuous blood pressure monitoring, occlusion plethysmography, and electrocardiography. Re-examination of patients was carried out by questioning and physical and laboratory examination. Results We found that fatal outcomes were associated with a lower Valsalva index (1.34 ± 0.16 vs. 1.69 ± 0.37, P < 0.05) and depressed cold vasoconstriction (0.20 ± 0.02 vs. 0.39 ± 0.16%, P < 0.05) and depressed cold vasoconstriction (0.20 ± 0.02 vs. 0.39 ± 0.16%, P < 0.05) and depressed cold vasoconstriction (0.20 ± 0.02 vs. 0.39 ± 0.16%, P < 0.05) and depressed cold vasoconstriction (0.20 ± 0.02 vs. 0.39 ± 0.16%, P < 0.05) and depressed cold vasoconstriction (0.20 ± 0.02 vs. 0.39 ± 0.16%, P < 0.05) and depressed cold vasoconstriction (0.20 ± 0.02 vs. 0.39 ± 0.16%, P < 0.05) and depressed cold vasoconstriction (0.20 ± 0.02 vs. 0.39 ± 0.16%, Conclusions This study shows that such autonomic regulation indices as Valsalva index, blood pressure dynamics in the tilt test, cold-stress vasomotor reactivity, and BPV are important for prognosis of hypertension course.

МЕДЛЕННАЯ ДИНАМИКА СТЕПЕНИ СИНХРОНИЗОВАННОСТИ КОНТУРОВ ВЕГЕТАТИВНОЙ РЕГУЛЯЦИИ РИТМА СЕРДЕЧНО-СОСУДИСТОЙ СИСТЕМЫ

Introduction: The main problem in analyzing low-frequency components of biological processes is conducting specialized experiments with long-term signal recording. However, the information about the system behavior on long scales can make an invaluable contribution to understanding the nature of the interaction between separate elements of the system. Purpose: Analyzing the features of the dynamics of the proposed quantitative index which characterizes the degree of phase synchronization of complex non-stationary biological systems (contours of autonomic regulation of the cardiovascular system) on time scales about tens and hundreds of characteristic oscillation periods (hundreds of seconds) using long experimental records. Results: During the experiments, we obtained simultaneous registration of two-hour signals from 23 healthy subjects: cardiointervalogram and photoplethysmogram vessels. The dynamics of the total percentage of phase synchronization (S index) of 0.1 Hz oscillations in the PPG and CIG was estimated in sliding windows. Similarly, we investigated the powers of so-called low-frequency (LF, 0.1 Hz) and high-frequency (HF, > 0.1 Hz) components of the spectrum of the original signals. The features of the interaction between the studied indices were evaluated using correlation analysis methods. We have found that the S index dynamics shows signs of its oscillatory nature with a characteristic oscillation period about 1000 s. The interaction between LF and HF oscillations in the autonomic circulatory regulation is of a complex nonlinear character. We have also identified signs of oscillations with a period about 1000 s in the dependencies of the total percentage of the phase synchronization of 0.1 Hz contours in circulatory regulation. A structural model of the interaction between circulatory regulatory contours is formed which explains the observed effects. Practical relevance: Obtaining fundamental knowledge about the interaction and regulation of the cardiovascular system elements will allow us to improve the methods we are developing for the diagnostics and therapy of pathological disturbances in the cardiovascular system.

Arterial hypertension in migraine: Role of familial history and cardiovascular phenotype

Recent studies indicate that migraine is associated with increased risk of cardiovascular diseases. However, links between autonomic cardiovascular regulation, arterial hypertension (AH) and migraine are still little explored. In this study, we evaluated autonomic regulation in migraine patients with and without hypertension. We studied 104 patients with migraine, aged 34±10 y, including 28 with and 76 without hypertension (M+AH and M-AH groups, respectively). The control group consisted of 88 healthy volunteers matched by age and sex. The autonomic regulation of circulation was examined with the tilt-table test, deep-breathing and Valsalva Maneuver, handgrip test, cold-stress induced vasoconstriction, arterial baroreflex, and blood pressure variability measurements. We found that migraine patients with concomitant hypertension demonstrated reduced arterial baroreflex, whereas other parameters of cardiac autonomic regulation were unchanged. In contrast, most indicators of vasomotor reactivity (blood pressure response to the hand-grip, Valsalva maneuver and cold vasoconstriction) were enhanced in migraine patients with no significant differences between migraine patients with and without hypertension. Patients from both M+AH and M-AH groups more commonly had a family history of cardiovascular disorders. Our data revealed increased vasomotor reactivity in migraine patients, with or without concomitant hypertension. This was associated with the family history of cardiovascular diseases.

MPS 06-05 FAMILY HISTORY OF CARDIOVASCULAR DISEASE AND AUTONOMIC REGULATION OF CIRCULATION IN MIGRAINEURS WITH AND WITHOUT CONCOMITANT HYPERTENSION

Objective: It has been reported that migraine patients are at greater risk of cardiovascular complications. We hypothesize that this may be caused by features of the autonomous regulation of blood flow and/or heredity of the cardiovascular disease (HCD). The purpose of the study is exploration of the links between the heredity of cardiovascular diseases and autonomic regulation in migraineurs with and without concomitant arterial hypertension. Design and Method: 103 patients with migraine (mean age 34.4 ± 10 y) including 27 patients with (M+H) and 76 patients without (M-H) hypertension have been examined. The control group consisted of 88 matched healthy volunteers. All participants were asked to fill up questionnaires concerning medical history of the closest relatives. Autonomic regulation of circulation was experimentally assessed by six different tests, which included tilt-table test (TT), a deep breathing (DB) and Valsalva Maneuver with estimation of the Valsalva index (VI) and mean-blood-pressure increment during the second phase (IBPVM), handgrip test (HG), cold-stress vasoconstriction (CSV), and arterial baroreflex (BRS). Results: We found that BRS was lower in the M+H group whereas no difference was found between M-H and control group. There were no differences in VI and DP among the groups. Moreover, dynamics of diastolic blood pressure during TT was higher in М+H group compare to both M-H and control group. However, three vasomotor parameters (IBPVM, HG, and CSV) were higher in both M+H and M-H groups compared to the control group. In addition, HCD was seen frequently in both migraine groups compare to the control group. Conclusions: Concomitant arterial hypertension in migraineurs is associated with additional reduction of BRS and orthostatic hypertension, but both heredity of cardiovascular disease and increased neurogenic vasomotor reactivity are more frequent in migraine patients regardless of hypertension.

Dose-Effect Relationship Between Mild Levels of Hypergravity and Autonomic Circulatory Regulation.

The dose-effect relationships between different levels of hypergravity (>+1.0 Gz) and steady-state hemodynamic parameters have been reported in several studies. However, little has been reported on the dose-effect relationship between hypergravity levels and estimates of autonomic circulatory regulation, such as heart rate variability, arterial pressure variability, and spontaneous cardiac baroreflex sensitivity. We investigated dose-effect relationships between hypergravity levels from +1.0 Gz to +2.0 Gz (Δ0.5 Gz) and autonomic circulatory regulation to test our hypothesis that autonomic circulatory regulation has a linear relationship with hypergravity levels. Using a short-arm human centrifuge, 10 healthy seated men were subjected to +1.0 Gz, +1.5 Gz, and +2.0 Gz hypergravity. We evaluated steady-state hemodynamic parameters and autonomic circulatory regulation indices. Heart rate variability, arterial pressure variability, and spontaneous cardiac baroreflex sensitivity between arterial pressure and R-R interval variabilities were assessed by spectral analysis, sequence analysis, and transfer function analysis. Steady-state heart rate, stroke volume, and sequence slope (indicating spontaneous cardiac baroreflex sensitivity in response to rapid changes in arterial pressure) showed linear correlations with increases in gravity (from +1.0 Gz to +2.0 Gz). On the other hand, steady-state cardiac output, steady-state systolic arterial pressure, and low-frequency power of diastolic arterial pressure (indicating peripheral vasomotor sympathetic activity) remained unchanged with gravity increases. Contrary to our hypothesis, the present study suggested that autonomic circulatory regulations show complex changes with hypergravity levels. Spontaneous cardiac baroreflex sensitivity reduces in a dose-dependent manner from +1.0 Gz to +2.0 Gz, whereas peripheral vasomotor sympathetic activity seems to be maintained.

Statins and the autonomic nervous system

Statins (3-hydroxy-3-methylglutaryl-CoA reductase inhibitors) reduce plasma cholesterol and improve endothelium-dependent vasodilation, inflammation and oxidative stress. A 'pleiotropic' property of statins receiving less attention is their effect on the autonomic nervous system. Increased central sympathetic outflow and diminished cardiac vagal tone are disturbances characteristic of a range of cardiovascular conditions for which statins are now prescribed routinely to reduce cardiovascular events: following myocardial infarction, and in hypertension, chronic kidney disease, heart failure and diabetes. The purpose of the present review is to synthesize contemporary evidence that statins can improve autonomic circulatory regulation. In experimental preparations, high-dose lipophilic statins have been shown to reduce adrenergic outflow by attenuating oxidative stress in central brain regions involved in sympathetic and parasympathetic discharge induction and modulation. In patients with hypertension, chronic kidney disease and heart failure, lipophilic statins, such as simvastatin or atorvastatin, have been shown to reduce MNSA (muscle sympathetic nerve activity) by 12-30%. Reports concerning the effect of statin therapy on HRV (heart rate variability) are less consistent. Because of their implications for BP (blood pressure) control, insulin sensitivity, arrhythmogenesis and sudden cardiac death, these autonomic nervous system actions should be considered additional mechanisms by which statins lower cardiovascular risk.

Blood pressure and heart rate changes during fibreoptic orotracheal intubation: a comparison of children and adults

Autonomic circulatory regulation and airway anatomy in children are significantly different from those in adults. There is no available published data to compare whether there is a clinically relevant difference in the haemodynamic responses to fibreoptic orotracheal intubation (FOI) under the same conditions between children and adults. In this randomized clinical study, we compared the blood pressure (BP) and heart rate (HR) changes during FOI in 40 children aged 3.5-9 yr and 40 adults aged 21-57 yr, ASA 1 scheduled for elective plastic surgery under general anaesthesia requiring orotracheal intubation. Anaesthesia was induced with intravenous (i.v.) injection of fentanyl and propofol, and face mask inhalation of isoflurane before FOI. Noninvasive BP and HR were recorded before induction (baseline values), after induction (postinduction values), at intubation and for 5 min after intubation at 1-min intervals. The percentage changes of BP and HR at each time point were calculated. In children and adults, HR at intubation and 1-3 min after intubation were significantly higher than baseline and postinduction values. In adults, BP at intubation increased significantly compared to the postinduction values but did not exceed baseline values. In children, BP at intubation and 1 min after intubation were significantly higher than postinduction and baseline values. As compared to adults, FOI caused a more significant pressor response in children. The percentage changes of BP at intubation and 1 min after intubation were larger in children than in adults. However, there was no significant difference in the percentage change of HR during the observation between children and adults. Under general anaesthesia, FOI might cause a more significant pressor response in children than in adults.

Prognostic evaluation of bradyarrhythmias and heart rate variability in endurance master athletes

To investigate the possible differences in autonomic regulation of circulation between endurance trained older subjects and older subjects who practiced moderate exercise, 10 elderly male endurance athletes, aged 65 ± 2.6 (group A), were compared with 12 male elderly subjects, aged 66 ± 3.7, who practiced moderate exercise (group B), and with a control group (group C) composed of 20 healthy younger male subjects aged 32 ± 2.3 who practiced moderate exercise. ECG holter monitoring and heart rate variability analysis data were col-lected. Episodes of heart rate below 40 beats/min were found in 4 subjects of groups A and in 1 subject of group C. The non-spectral indexes used to analyze heart rate variability are significantly higher in athletes of group A and in subjects of group C than in subjects of group B. The results of spectral analysis are in keeping with a sympathetic prevalence during the day and a vagal pre-dominance during the night, but there was lower vagal activity during the night and higher adrenergic activity during the day in sedentary subjects. Older en-durance athletes seem to have more profound bradyarrhythmias than healthy elderly controls, but the age-related decrease in heart rate variability seems to be retarded. This may have a positive prognostic value, as it may decrease the risk of life threatening ventricular arrhythmias.

Impact of long-term therapy with eprosartan on the structural and functional state of the heart and large vessels and on the autonomic regulation of circulation in patients with arterial hypertension

To examine the effects of eprosartan on the remodelling of the heart and large vessels, on endothelial dysfunction and autonomic circulatory regulation in patients with hypertensive disease, thirteen patients were included into the study: Doppler echocardiographic study and evaluation of left ventricular diastolic function were performed on a Vingmed CFM800 apparatus: the thickness of the carotid intima-media complex and the diameter of the brachial artery were determined on the same apparatus using a 7.5-MHz transducer in the reactive hyperemia test. Automatic balance was evaluated by the spectral assay of cardiac rhythm variations. The cardiopulmonary component of baroreflex was also tested. Blood pressure normalized in 3 patients following 24 weeks of therapy with eprosartan in a daily dose of 600 mg. Two patients were excluded due to therapeutic inefficiency. In the remaining patients, the antihypertensive effect was incomplete. The mass of the left myocardial myocardium decreased by 10.8%. there was an increase in brachial arterial dilatation in the reactive hyperemia test. The variations of cardiac rhythm were not significantly changed, the baroreflex tended to be decreased. Thus, long-term eprosartan therapy improves the structural and functional state of the heart and vessels and fails to affect the autonomic regulation of circulation.

The significance of physical activity on the physiological stress reaction

The extent of physical activity and the dynamic performance capacity show an inverse relationship to cardiovascular mortality, independent of the influence of other risk factors, but the underlying mechanism remains uncertain. Most concepts assume that the aerobic capacity of the peripheral musculature is increased by training, and thus improved cardiocirculatory regulation and especially a more favorable stress reaction pattern are attained. This adaptation is essentially an inverse adaptation mechanism as in established cardiocirculatory insufficiency. Based on an extended stress concept, it can be seen that training effects, especially in autonomic circulatory regulation, occur under physiological conditions to a lower degree in the renin-angiotensin-aldosterone system and in inflammatory reaction. The training effects depend on the form of exercise, the baseline condition, the extent of training, and genetic predisposition. It can be particularly demonstrated when the aerobic capacity has been sufficiently enlarged in an adequate proportion of the peripheral musculature. To what extent and under what conditions these training effects can be used under the pathophysiological conditions of established cardiocirculatory insufficiency is presently under investigation.

Autonomic regulation of circulation and cardiac contractility during a 14-month space flight

The space flight of physician cosmonaut V.V. Polyakov, the longest to date (438 days), has yielded new data about human adaptation to long-term weightlessness. Autonomic regulation of circulation and cardiac contractility were evaluated in three experiments entitled Pulstrans, Night, and Holter. In the Pulstrans experiment electrocardiographic (ECG), ballistocardiographic (BCG), seismocardiographic (SCG), and some other parameters were recorded. In the Night experiment, only the ballistocardiogram was recorded, but a special feature of this experiment is that the BCG records were obtained with a contactless method. This method has several advantages, the most important of which are the possibility of studying slow-wave variations in physiologic parameters (ultradian rhythms) on the basis of recordings made under standard conditions over a prolonged period. The Holter experiment (24-hour electrocardiographic monitoring) used a portable cardiorecorder (Spacelab, USA). The obtained electrocardiographic data were used to analyze heart rate variability. In the first 6 months of the 14-month flight, the dynamics of cardiovascular parameters in V.V.Polyakov was virtually the same as in the other cosmonauts. The data obtained after the first 6 months of Polyakov's sojourn in space are unique and mention should be made of at least three important aspects: 1. (1) activation of a new, additional adaptive mechanism in the 8th–9th months of flight, as is evidenced by alterations in the periodicity and power of superslow wave oscillations (ultradian rhythms) reflecting the activity of the subcortical cardiovascular centers and of the higher levels of autonomic regulation; 2. (2) growth of cardiac contractility accompanied by a decrease in heart rate during the last few months of flight; 3. (3) a considerable increase in the daily average values of absolute power of heart rate's variability MF component, which reflects the activity of the vasomotor center. Specific mechanisms of adaptation to weightless conditions appear to be associated with activation of higher autnomic centers. The hypothesis that central levels of circulation regulation are activated in a long-term space flight was investigated by analyzing of ultradian rhythms in nighttime. The data, received during the flight of V. V. Polyakov, show, that the process of human adaptation to long influence of weightlessness consists of a number of consecutive stages, during which the activation of more and more high levels of control system of physiological functions occurs.

A study of the hemodynamic effects of varying the duration of inhalation and exhalation periods

The space flight of physician cosmonaut V.V. Polyakov, the longest to date (438 days), has yielded new data about human adaptation to long-term weightlessness. Autonomic regulation of circulation and cardiac contractility were evaluated in three experiments entitled Pulstrans, Night, and Holter. In the Pulstrans experiment electrocardiographic (ECG), ballistocardiographic (BCG), seismocardiographic (SCG), and some other parameters were recorded. In the Night experiment, only the ballistocardiogram was recorded, but a special feature of this experiment is that the BCG records were obtained with a contactless method. This method has several advantages, the most important of which are the possibility of studying slow-wave variations in physiologic parameters (ultradian rhythms) on the basis of recordings made under standard conditions over a prolonged period.The Holter experiment (24-hour electrocardiographic monitoring) used a portable cardiorecorder (Spacelab, USA). The obtained electrocardiographic data were used to analyze heart rate variability.In the first 6 months of the 14-month flight, the dynamics of cardiovascular parameters in V.V.Polyakov was virtually the same as in the other cosmonauts. The data obtained after the first 6 months of Polyakov's sojourn in space are unique and mention should be made of at least three important aspects: 1.(1) activation of a new, additional adaptive mechanism in the 8th–9th months of flight, as is evidenced by alterations in the periodicity and power of superslow wave oscillations (ultradian rhythms) reflecting the activity of the subcortical cardiovascular centers and of the higher levels of autonomic regulation;2.(2) growth of cardiac contractility accompanied by a decrease in heart rate during the last few months of flight;3.(3) a considerable increase in the daily average values of absolute power of heart rate's variability MF component, which reflects the activity of the vasomotor center.Specific mechanisms of adaptation to weightless conditions appear to be associated with activation of higher autnomic centers. The hypothesis that central levels of circulation regulation are activated in a long-term space flight was investigated by analyzing of ultradian rhythms in nighttime.The data, received during the flight of V. V. Polyakov, show, that the process of human adaptation to long influence of weightlessness consists of a number of consecutive stages, during which the activation of more and more high levels of control system of physiological functions occurs.

Reversal of adaptive left ventricular atrophy following electrically-stimulated exercise training in human tetraplegics

Left ventricular (LV) myocardial atrophy and diminished cardiac function have been shown to accompany chronic human tetraplegia. These changes are attributable both to physical immobilisation and abnormal autonomic circulatory regulation imposed by a spinal cord injury (SCI). To test whether exercise training increases LV mass following chronic SCI, 8 neurologically complete quadriplegic males at 2 SCI rehabilitation and research centres underwent one month of electrically-stimulated quadriceps strengthening followed by 6 months of electrically-stimulated cycling exercise. Resting M-mode and 2-D echocardiograms were measured before and after exercise training to quantify the interventricular septal and posterior wall thicknesses at end-diastole (IVSTED and PWTED, respectively), and the LV internal dimension at end-diastole (LVIDED). LV mass was computed from these measurements using standard cube function geometry. Results showed a 6.5% increase in LVIDED following exercise training (p less than 0.02), with increases in IVSTED and PWTED of 17.8 (p less than 0.002) and 20.3% (p less than 0.01), respectively. Computed LV mass increased by 35% following exercise training (p = 0.002). These data indicate that myocardial atrophy is reversed in tetraplegics following electrically-stimulated exercise training, and that the changes in cardiac architecture are likely to be the result of both pressure and volume challenge to the heart imposed by exercise.

Autonomic circulatory regulation in uremia (author's transl)

Uremic autonomic neuropathy leads to impaired function of the baroreflex. The main defect, according to literature, is located in the afferent limb of the reflex arc and in the efferent cardiac vagus nerve, whereas the sympathetic part of the efferent arc is still intact. Own results, obtained in hemodialysis patients during orthostasis and volume removal induced sympathetic stimulation, showed qualitatively and quantitatively adequate sympathetic response and also an adequate end organ receptor response. Autonomic nervous neuropathy predisposes to volume removal related symptomatic hypotension during hemodialysis treatment. In addition hemodialysis treatment per se induces a so far unexplained interference with sympathetic response to volume removal. The autonomic neuropathy also predisposes to development of hypertension in response to volume load.