Parasympathetic Cardiovascular Control Research Articles

Maladaptive Cardiac Autonomic Control during a Stress Reactivity Assessment Among Primary Care Patients with Metabolic Syndrome.

Metabolic syndrome (MetS) comprises a constellation of metabolic abnormalities that substantially increase risk for chronic illnesses. Autonomic dysregulation is closely linked to MetS, and while pathophysiological models often address chronic stress exposure, none have examined how such physiological contributions operate situationally, in a clinical setting. We used ambulatory impedance cardiography to examine indicators of cardiac autonomic control (CAC) in a sample of 50 adult primary care patients with and without MetS. Indices of independent sympathetic and parasympathetic cardiovascular control in primary care outpatients were measured during a brief stress reactivity assessment. We compared interdependent CAC features, including cardiac autonomic balance (i.e., sympathovagal reciprocity) and cardiac autonomic regulation (i.e., sympathovagal coactivation) and found significant differences among MetS participants as compared to healthy controls. In particular, cardiac autonomic regulation scores were higher among MetS patients when discussing medication concerns, and cardiac autonomic balance scores were lower among MetS patients when discussing daily stressors. These results suggest that patients meeting criteria for MetS demonstrate momentary variations in CAC depending on personally relevant health topics. The potential for future research is discussed with a focus on prospective data collection to enhance diagnostic procedures and treatment monitoring.

Blood pressure reduction after gastric bypass surgery is explained by a decrease in cardiac output.

The reason for the decrease in blood pressure (BP) in the first weeks after gastric bypass surgery remains to be elucidated. We show that the reduction in BP following surgery is caused by a decrease in cardiac output. In addition, the maximal ascending slope in systolic blood pressure decreased suggesting a reduction in left ventricular contractility and cardiac workload. These findings help to understand the physiological changes following gastric bypass surgery and are relevant in light of the increased risk of heart failure in these patients.

Fit elderly men can also stand: orthostatic tolerance and autonomic cardiovascular control in elderly endurance athletes.

Endurance training may reduce orthostatic tolerance. Elderly people are prone to orthostatic intolerance, but the impact of endurance training in old age has been insufficiently explored. 54 healthy men; 30 endurance athletes and 24 controls, free from medication and chronic diseases, were subjected to head-up tilt tests: 30º for 10min and 70º for 40min. Non-invasive recordings of blood pressures, heart rate, stroke volume, end diastolic volume, total peripheral resistance, heart rate variability, blood pressure variability, and baroreflex sensitivity were obtained. We registered terminations of test due to frank syncope or unbearable presyncopal symptoms. Mean age 71years (range 65-84); athletes had lower body mass index (23.4 versus 24.8, p<0.05) and lower resting heart rate (50 versus 61, p<0.01). Blood pressures and total peripheral resistance were equal. End diastolic volume index, baroreflex sensitivity, and heart rate variability were higher among athletes, both HF-RRI (high-frequency variability, reflecting parasympathetic activity) and LF-RRI (low-frequency variability, reflecting both sympathetic and parasympathetic activity). Syncope or presyncopal symptoms occurred in 11 persons, 4 athletes and 7 controls (p=0.2). Cox Regression analysis showed that higher heart rate at rest was the only variable associated with syncope. Orthostatic tolerance was not reduced among elderly endurance athletes. Rather, there was a trend towards better orthostatic tolerance, which might be attributed to stronger parasympathetic cardiovascular control and larger blood volume. Better orthostatic tolerance might be an additional benefit of physical activity in older age.

Is a Mindfulness Score Differentially Associated with Parasympathetic Cardiovascular Control in Persons with and without a Meditation-Related Practice?

Is a Mindfulness Score Differentially Associated with Parasympathetic Cardiovascular Control in Persons with and without a Meditation-Related Practice?

Nocturnal cardiac autonomic regulation in Parkinson's disease.

Diminished heart rate (HR) variability has been reported in patients with early phase Parkinson's disease (PD) using standardized cardiovascular reflex tests. However, limited data exist on HR variability during sleep; thus the present study was performed to investigate the characteristics of HR variability during different sleep stages. The HR variability of 21 newly diagnosed and untreated PD patients and of 22 control subjects was evaluated by using time domain, frequency domain and non-linear methods and by analyzing HR reactions to body movements during the different sleep stages (non-REM stages S1-4 and the REM stage). The nocturnal cardiac autonomic control was disturbed in PD patients compared to controls both during sleep and waking. HR reactions to body movements were decreased especially during REM sleep referring to defective sympathetic cardiovascular control. High frequency spectral power of HR variability was attenuated in the patients in waking and during non-REM sleep but not during REM sleep suggesting that parasympathetic cardiovascular control is also affected in early PD. However, the variance of R-R intervals during non-REM sleep was significantly increased in PD patients. Especially during this sleep stage the patients also moved more than the controls. HR variability is decreased not only in waking but also during sleep in PD patients. However, the increased variance of HR during non-REM sleep refers that in early phase of PD cardiovascular system is still able to react to changing body circumstances. Furthermore, our findings suggest that the indicators measuring the dominant sympathetic or parasympathetic activity of each given sleep stage are the most sensitive measures in revealing disturbed nocturnal ANS function.

Anxiety and autonomic regulation in major depressive disorder: an exploratory study

Spectral analysis of fluctuations in heart rate and blood pressure was employed to explore sympathetic and parasympathetic cardiovascular control mechanisms in relation to trait anxiety in major depressive disorder. Sixteen drug-free female depressed patients were divided into two groups: those who were high on trait anxiety (HTA, n = 9) and those who were normal or low on trait anxiety (LTA, n = 7). In patients and age-matched female controls ( n = 10), heart rate (HR), blood pressure (BP; Finapres device) and respiration were recorded during a period of supine rest (10 min), orthostatic challenge (60 ° head-up tilting, 8 min), and post-orthostatic supine rest (8 min). Power spectra were calculated over the last 4 min of these three situations for HR, systolic BP, as well as for respiration. Spectral density was assessed for three frequency bands: low (0.02–0.06 Hz), mid (0.07–0.14 Hz) and high (0.15–0.50 Hz). Patients did not differ from controls during supine rest. During orthostatic challenge, HTA patients showed significantly more HR increase and suppression of high-frequency fluctuations of HR (suggesting stronger vagal inhibition) in comparison with the controls; this effect was accompanied by a significant increase in respiratory frequency. Both patients groups did not show the normal increase in mid-frequency band fluctuations of BP during orthostatic challenge, indicating reduced sympathetic activation. Low-frequency fluctuations of HR, as well as respiratory frequency during post-orthostatic supine rest of the HTA patients were significantly increased versus controls. This exploratory study indicates that trait anxiety may be a relevant factor when evaluating parasympathetic and sympathetic dysbalances in the state of a major depressive disorder.

Decreased heart rate variability in amyotrophic lateral sclerosis.

Autoregressive spectral analysis of heart rate variability (HRV) was performed in 29 patients with amyotrophic lateral sclerosis (ALS) and 33 age-matched healthy subjects to evaluate the involvement of the autonomic nervous system. HRV analysis provides a means to recognize low (LF) and high (HF) frequency components, respectively mediated by sympathetic and parasympathetic heart control. An increase in the mean heart rate at rest (P < 0.001), a decrease in standard deviation of R-R interval as well as in PNN50 (P < 0.001), and an increase in the LF/HF component ratio (P < 0.01) were found in the ALS patients, indicating a vagal-sympathetic imbalance. These alterations were not related to the clinical features and to the duration of the disease. Our results suggest a subclinical involvement of the autonomic nervous system in ALS, particularly affecting parasympathetic cardiovascular control.

Psychophysiological measures of workload during continuous manual performance.

Twelve subjects (six female) participated in an experiment designed to separate the effects of perceptual/central and physical demands on psychophysiological measures of peripheral nervous system activity. The difficulty of a single-axis continuous manual tracking task was varied in two ways: order of control was manipulated to vary perceptual/central processing demand, and disturbance amplitude was manipulated to vary physical demand. Physiological measures were sensitive to the imposition of a task and were more sensitive to physical than to perceptual/central demands. A principal components analysis identified five factors (three of them physiological) that accounted for 83.1% of the observed variance. Perceptual/central processing demands specifically affected the component identified with sympathetic cardiovascular control, whereas physical demands were reflected in the component identified with parasympathetic cardiovascular control. This finding suggests that dissociations observed among cardiovascular measures in manual performance tasks are attributable to differential activation of the autonomic control systems.

Reduced parasympathetic cardiac control in patients with hypertension at rest and under mental stress

The neurogenic component in the pathogenesis of essential hypertension has predominantly been analyzed with regard to the sympathetic part of the autonomous nervous system; the parasympathetic branch has largely been neglected. We investigated whether 54 normotensive (mean casual blood pressure [cBP]: 125 ± 6 82 ± 4 mm Hg), 41 borderline hypertensive (cBP: 134 ± 8 90 ± 5 mm Hg), and 34 hypertensive men (cBP: 152 ± 13 101 ± 5 mm Hg) without secondary target organ damage differed in parasympathetic cardiac control. Parasympathetic cardiac control was assessed via the amount of fast fluctuations (0.15 to 0.40 Hz; vagus band) and by the amount of respiratory-linked fluctuations (mean respiratory frequency ± 0.03 Hz) in the power spectra of continuously registered interbeat intervals under the following conditions: mean of three rest phases with 10, 5, and 5 minutes' duration (REST); mean of two modes of a reaction time task with 10 and 5 minutes' duration (RTT); mean of 5 minutes' mental arithmetic plus noise (MA). Analysis of variance (ANOVA) shows that spectral energy in the so-called vagus band reveals the most prominent differences between blood pressure groups under all conditions: REST = normotensive, 2.70 ± 0.31; borderline hypertensive, 2.55 ± 0.33; and hypertensive, 2.43 ± 0.43 (F[2.126] = 6.19; p < 0.01). RTT = normotensive, 2.41 ± 0.35; borderline hypertensive, 2.19 ± 0.33; and hypertensive, 2.17 ± 0.46 (F[2.126] = 6.04; p < 0.01); MA = normotensive, 2.69 ± 0.34; borderline hypertensive, 2.52 ± 0.33; and hypertensive, 2.38 ± 0.46 (F[2.126] = 7.04; p < 0.01). The ratio between the midfrequency band around 0.10 Hz and the vagus band, tentatively representing sympathovagal balance, is increased in both nonnormotensive groups, indicating a relative preponderance of sympathetic efferents. The results demonstrate that a reduction in parasympathetic cardiac control significantly contributes to a disturbance in sympathetic and parasympathetic cardiovascular control in hypertension.

Autonomic functions in the early stages of Parkinson's disease.

Disturbances of autonomic nervous functions are common in patients with Parkinson's disease (PD) and may develop as a result of pathological changes in centers of autonomic regulation such as the hypothalamus, brainstem, and sympathetic ganglia. We examined cardiovascular reflexes using bedside, noninvasive procedures in 20 unmedicated PD patients with early stages of the disease (stage 1 and 2 on the Hoehn and Yahr's scale). Sixteen patients (80%) exhibited some degree of autonomic nervous system dysfunction. These included predominantly cardiovascular functions mediated via the parasympathetic system. Our findings demonstrate: (a) a high prevalence of autonomic disturbances in early stage PD, and (b) that dysregulation of parasympathetic cardiovascular control mechanisms is a major feature of dysautonomia in early, unmedicated PD patients.

Cardiovascular autonomic reflexes in mid-pregnancy.

To study the physiological responses to noninvasive cardiovascular autonomic function tests in normal pregnancy. Cardiovascular autonomic responses in 60 women at 22 to 29 weeks gestation and 62 nonpregnant women were investigated using the Valsalva manoeuvre as well as orthostatic, quiet breathing, deep breathing, and isometric handgrip tests. Compared with nonpregnant women, those who were pregnant showed significantly lower heart rate variability during normal breathing and a blunted tachycardic reaction to blowing during the Valsalva manoeuvre. The vagally controlled biphasic heart rate response to standing was also attenuated in the pregnant group. The cardiovascular responses were blunted in mid-pregnancy indicating a decrease in parasympathetic cardiovascular control.

Autonomic functions in the early stages of Parkinson's disease.

Disturbances of autonomic nervous functions are common in patients with Parkinson's disease (PD) and may develop as a result of pathological changes in centers of autonomic regulation such as the hypothalamus, brainstem, and sympathetic ganglia. We examined cardiovascular reflexes using bedside, noninvasive procedures in 20 unmedicated PD patients with early stages of the disease (stages 1 and 2 on the Hoehn and Yahr's scale). Sixteen patients (80%) exhibited some degree of autonomic nervous system dysfunction. These included predominantly cardiovascular functions mediated via the parasympathetic system. Our findings demonstrate: (a) a high prevalence of autonomic disturbances in early stage PD, and (b) that dysregulation of parasympathetic cardiovascular control mechanisms is a major feature of dysautonomia in early, unmedicated PD patients.

Effect of enalapril on parasympathetic activity

To evaluate the effect of converting enzyme inhibition induced by enalapril on parasympathetic activity, we studied ten essential hypertensive patients, age range 38-58 years, WHO I-II. Parasympathetic evaluation was obtained by measuring the variation of heart period (VHP) during at least 1 minute of steady-state, regular respiration. VHP was derived from the difference between the mean of all maximum and the mean of all minimum heart periods. The higher the VHP, the higher the parasympathetic control of heart rate and vice versa. VHP was measured supine and with tilting (30 degrees, 60 degrees, 85 degrees). Blood pressure was reduced after 1 month of enalapril treatment, while the heart rate did not change. VHP increased at the end of enalapril treatment compared with placebo: in the supine position it increased from 36 +/- 3.2 ms to 44 +/- 3.5 ms, p less than 0.01. VHP was also increased by enalapril at 30 degrees (p less than 0.05) and 60 degrees (p less than 0.05), while no difference was observed at 85 degrees between placebo and enalapril. A positive correlation was found between supine enalapril changes of VHP and those of systolic and diastolic BP. In conclusion, enalapril seems to increase parasympathetic cardiovascular control in essential hypertensive patients. This result might explain the lack of increase in heart rate that would be expected as a result of the vasodilating effect of enalapril.

Parasympathetic cardiovascular control in human disease: a critical review of methods and results.

A variety of experimental approaches have been used to alter reflex parasympathetic cardiovascular control in normal human subjects and in patients with cardiovascular diseases. This review critically appraises several of these methods (the Valsalva maneuver, upright tilt, lower body negative pressure, pressor drug infusion, neck suction, and coronary arteriography) and summarizes the normal response patterns of healthy subjects and the abnormal response patterns of some patients with cardiovascular disease. Tests of parasympathetic function tend to be heterogeneous; they are not standardized, and, therefore, valid comparisons between results from different studies may be difficult to make. Moreover, although most of these tests are simple to perform, they may provoke surprisingly complex alterations of afferent and efferent autonomic activity. Notwithstanding these methodological difficulties, the research area of human parasympathetic cardiovascular control may have great importance, because parasympathetic reflex mechanisms are involved in diseases of major public health significance for which animal models may be imperfect or nonexistent.