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PubMedDate not supplied

Age-related modifications of heart rate during sleep-wakefulness cycle.

Twenty-four-hour monitoring of heart rate is currently used in cardiological practice, but it has been rarely applied to investigate the autonomic nervous system functioning. In the present study we investigated the heart rate of 275 healthy subjects, aged 15-69 years, divided into 11 groups by 5-year periods of age. Our results suggest that the balance between parasympathetic and sympathetic activities changes with advancing age. The parasympathetic activity becomes stronger and during sleep loses its power to modulate bradycardia. The general conclusion of our study is that all the investigations on cardiac autonomic functions are to be performed on age-matched basis.

Adolescent↗
PubMed1991

Severity of coronary atherosclerosis correlates with the respiratory component of heart rate variability.

Decreased vagal activity is frequently observed in coronary artery disease, but the mechanism of this association is unknown. We investigated cardiac autonomic function by relating heart rate spectral components to clinical and angiographic findings in 80 patients who were undergoing coronary angiography. The age- and sex-adjusted magnitude of the respiratory spectral component, which is an index of cardiac vagal tone, showed a significant negative correlation with the extent of coronary atheromatosis (r = -0.43, p less than 0.0001) and a less significant negative correlation with the severity of coronary stenosis (r = -0.30, p = 0.0070). These relationships were independent of previous myocardial infarction and of left ventricular function. Stepwise regression analysis showed that the respiratory spectral component contributed to atheromatosis independently of established coronary risk factors (partial R2 = 9.4%, p = 0.002), but not to stenosis. Our results support the hypothesis that decreased cardiac vagal activity is associated with an increased risk of coronary atherosclerosis.

Adult↗
PubMedDate not supplied

Autonomic function in patients on continuous ambulatory peritoneal dialysis.

OBJECTIVE: To investigate sympathetic function in the peripheries of patients on chronic ambulatory peritoneal dialysis (CAPD) using noninvasive techniques. DESIGN: Comparison of peripheral blood flow responses in sympathetic vasoconstrictor reflexes in CAPD patients and matched control subjects. SETTING: Tertiary care hospital and research institution. PATIENTS: Twenty-three clinically stable CAPD patients and 23 control subjects matched for age, sex, and drug therapy. MAIN OUTCOME MEASURES: Sympathetic activity assessed from the reductions in hand and foot blood flow induced by a deep breath and by body surface cooling. Cardiac autonomic activity measured by the changes in heart rate produced by deep breathing, a Valsalva maneuver, and standing from lying. RESULTS: A deep breath induced mean decreases in hand blood flow of 65.1% in the patients and 82.8% in their matched controls. Corresponding reductions in the foot were 46.0% and 70.0%. Body surface cooling reduced mean hand blood flow by 50.3% in the patients and 71.8% in the control subjects. Corresponding values in the foot were 26.7% and 43.6%. The differences in response between the patients and their matched control subjects were all significant (p < 0.01). Cardiac autonomic function assessed by standard tests of heart rate variability was significantly impaired in the patients compared with the control subjects in two of the three tests used (p < 0.001). CONCLUSIONS: Cardiovascular autonomic impairment can affect the peripheral circulation as well as the heart in patients on dialysis, and this may have implications for cardiovascular homeostasis.

Adult↗
PubMed1993

Autonomic function in neuropathic diabetic patients with foot ulceration.

OBJECTIVE: The aim of this study was to compare peripheral autonomic function in neuropathic diabetic subjects with and without foot ulceration. RESEARCH DESIGN AND METHODS: Measurements were made on 57 diabetic subjects; 35 subjects had evidence of peripheral neuropathy, 14 of these had a history of foot ulceration, and 22 subjects had no evidence of peripheral neuropathy. No patient had peripheral vascular disease. Measurements were made of motor and sensory nerve conduction. Autonomic function was investigated by using standard cardiovascular reflex tests and by measuring blood flow variability in the foot. The vasoconstrictor responses to deep breathing and body cooling were measured by using venous occlusion plethysmography. RESULTS: Peripheral sympathetic function was significantly worse in the DU group. The vasoconstrictor response to deep breathing in the DU group was significantly smaller than the response in the DN group (15.3 +/- 2.7 vs. 38 +/- 4%, P < 0.001). The response to body cooling in the DU group was significantly smaller than the response in the DN group (6.2 +/- 3.1 vs. 20.8 +/- 3.5%, P < 0.01). Tests of cardiac autonomic function and measurements of motor and sensory nerve conduction were similar in both neuropathic groups. CONCLUSIONS: Peripheral autonomic neuropathy is associated with the development of foot ulceration in diabetic subjects.

Autonomic Nervous System↗
PubMed2006

Correlation between striatal dopamine D2/D3 receptor binding and cardiovascular activity in healthy subjects.

BACKGROUND: The relationship between the striatal dopaminergic system and cardiovascular activity is not well known. The aim of this study is to investigate the relationship between striatal D2/D3 receptor binding and cardiovascular activity. METHODS: The striatal D2/D3 receptor binding of 34 healthy volunteers was assessed by the single-photon emission computed tomography (SPECT) imaging method with the [123I]-iodobenzoamide (IBZM) ligand. The ratio of the radioactivity in the striatum (St) and the frontal cortex (Fc) (St/Fc ratio) was used as the marker for striatal D2/D3 receptor binding. Their cardiac autonomic functions were measured by continuously monitoring their heart rate and blood pressure (BP) in supine position during 10 min. The heart rate variability (HRV) was analyzed by spectral analysis and the geometric method. RESULTS: The St/Fc ratio of striatal dopamine D2/D3 receptor binding correlated negatively with heart rate (HR), and positively with cardiac vagal index (CVI) and low frequency (LF) power in healthy subjects who were in a supine resting position. CONCLUSIONS: Striatal dopamine D2/D3 receptors may play a part in cardiovascular regulation.

Adult↗
PubMed2006

HFE genotype, particulate air pollution, and heart rate variability: a gene-environment interaction.

BACKGROUND: Particulate air pollution has been associated with cardiovascular mortality and morbidity. Transition metals such as iron bound to the particles may be responsible for those associations. The protein product of the hemochromatosis (HFE) gene modulates uptake of iron and divalent cations from pulmonary sources and reduces their toxicity. Two HFE polymorphisms (C282Y and H63D) associated with increased iron uptake may modify the effect of metal-rich particles on the cardiovascular system. METHODS AND RESULTS: We investigated the association between particulate matter < or = 2.5 microm in aerodynamic diameter and heart rate variability in 518 older men from the Normative Aging Study who were examined between November 2000 and December 2004. Linear regression models were fit to evaluate interactions between HFE genotype and particulate matter < or = 2.5 microm in aerodynamic diameter in relation to heart rate variability, controlling for potential confounders. A 10-microg/m3 increase in particulate matter < or = 2.5 microm in aerodynamic diameter during the 48 hours before heart rate variability measurement was associated with a 31.7% (95% CI, 10.3% to 48.1%) decrease in the high-frequency component of heart rate variability in persons with the wild-type genotype, whereas no relationship in the high-frequency component was observed in persons with either HFE variant. The difference in effect of particulate matter < or = 2.5 microm in aerodynamic diameter on the high-frequency component between persons with and without HFE variants was significant (P for interaction=0.02). CONCLUSIONS: The effect of particles on cardiac autonomic function was shielded in subjects with at least 1 copy of an HFE variant compared with wild-type subjects. Transition metals, including iron, bound to ambient particles and the related oxidative stress may play an important role in cardiac toxicity of particles.

Adult↗
PubMed1998

Glucose-induced thermogenesis, inhibition of lipid oxidation rate and autonomic dysfunction in non-diabetic obese women.

OBJECTIVE: The aim of this study was to look for a relationship between autonomic dysfunction and alterations in glucose- induced thermogenesis (GIT) and lipid oxidation rate in obese non-diabetic women. SUBJECTS: 37 obese women, 20 with impaired cardiac autonomic function tests (group 1) were matched with 17 women with normal tests (group 2) according to age, weight, body mass index (BMI), waist-to-hip ratio (WHR), fat mass (FM) and fat free mass (FFM). MEASUREMENTS: A series of five standardized tests was carried out, three of which were based mainly on cardiac parasympathetic control (heart rate response to Valsalva, deep breathing and lying-to-standing) and two on cardiovascular sympathetic function (blood pressure response to standing and to handgrip). Energy expenditure (EE), lipid and glucose oxidation rate were determined by indirect calorimetry at fasting and after an oral glucose load (75 g). Blood glucose, insulin and catecholamines responses to glucose were examined. RESULTS: There was no significant difference in plasma glucose, insulin, catecholamines, metabolic rate, glucose and lipid oxidation rate at fasting and plasma glucose, insulin and catecholamine responses to glucose. GIT was slightly but not significantly lower in group 1 (24.7+/-10.4 kJ) than in group 2 (46.8+/-9.0 kJ). The cumulative glucose oxidation rate did not differ significantly in the two groups. The cumulative lipid oxidation rate was significantly lower in group 1 than in group 2 (-49.4+/-4.1 vs -30.8+/-8.0, respectively, P = 0.033). It correlated negatively with the area under the curve of insulin response (r=-0.37, P=0.04). In the multivariate analysis, both autonomic dysfunction and the area under the curve of insulin response correlated significantly with the cumulative lipid oxidation rate. CONCLUSION: This study suggests that 1) the glucose-induced inhibition of the lipid oxidation rate in obese women is greater in the patients with autonomic dysfunction; 2) a decrease in sympathetic activity is likely to be involved in this phenomenon.

Adolescent↗
PubMedDate not supplied

[Temporal analysis of cardiac frequency variability in basal condition in elderly chagasic subjects in indeterminate form in endemic área].

With the aim of evaluating the cardiac autonomic function in elderly chagasic patients living in an endemic area, we evaluated, by using computadorized heart rate variability, 28 elderly chagasic with the indeterminate form, 28 elderly non chagasic and 28 young healthy control. In all patients we performed conventional electrocardiogram, radiological investigation of thorax, and with contrast of esophagus and colons and echodopplercardiogram. Non chagasic patients did not perform only the exams with contrast. The systolic ventricular function was preserved in all subjects. There was no statistically significant difference between the groups with regard to mean duration of RR intervals. Considering the variance, standard deviation, variation coefficient and pNN50 there was statistically significant difference between the young and elderly groups but no difference was found when the analysis was performed in each one separately for these temporal indexes. We conclude that, in basal condition, the groups of elderly chagasic and no chagasic subjects did not differ as much as the cardiac autonomic modulation in time domain.

Adult↗
PubMed2002

Major depression with ischemic heart disease: effects of paroxetine and nortriptyline on measures of nonlinearity and chaos of heart rate.

Depression is associated with increased cardiovascular mortality in patients with preexisting cardiac illness. A decrease in cardiac vagal function as suggested by a decrease in heart rate variability (HRV) or heart period variability has been linked to sudden death in patients with cardiac disease as well as in normal controls. Recent studies have shown decreased vagal function in cardiac patients with depression as well as in depressed patients without cardiac illness. In this study, we compared 20 h awake and sleep heart period nonlinear measures using quantification of nonlinearity and chaos in two groups of patients with major depression and ischemic heart disease (mean age 59-60 years) before and after 6 weeks of treatment with paroxetine or nortriptyline. Patients received paroxetine, 20-30 mg/day or nortriptyline targeted to 190-570 nmol/l for 6 weeks. For HRV analysis, 24 patients were included in the paroxetine treatment study and 20 patients in the nortriptyline study who had at least 20000 s of awake data. The ages of these groups were 60.4 +/- 10.5 years for paroxetine and 60.8 +/- 13.4 years for nortriptyline. There was a significant decrease in the largest Lyapunov exponent (LLE) after treatment with nortriptyline but not paroxetine. There were also significant decreases in nonlinearity scores on S(netPR) and S(netGS) after nortriptyline, which may be due to a decrease in cardiac vagal modulation of HRV. S(netGS) and awake LLE were the most significant variables that contributed to the discrimination of postparoxetine and postnortriptyline groups even with the inclusion of time and frequency domain measures. These findings suggest that nortriptyline decreases the measures of chaos probably through its stronger vagolytic effects on cardiac autonomic function compared with paroxetine, which is in agreement with previous clinical and preclinical reports. Nortriptyline was also associated with a significant decrease in nonlinearity scores, which may be due to anticholinergic and/or sympatholytic effects. As depression is associated with a strong risk factor for cardiovascular mortality, one should be careful about using any drug that adversely affects cardiac vagal function.

Aged↗
PubMed2003

Effect of fluoxetine, pemoline and placebo on heart period and QT variability in normal humans.

OBJECTIVE: To measure the effects of fluoxetine and pemoline on heart period and QT variability. METHODS: Healthy volunteers were randomly assigned treatment with 20 mg daily of fluoxetine (n=7), 56.25 mg of pemoline (n=7) or placebo (n=9). Twenty-four-hour Holter ECGs were obtained before and after approximately 8 weeks of double-blind treatment. RESULTS: There were no significant changes in the fluoxetine group. Pemoline was associated with a significant decrease in the high frequency (HF) power (0.15-0.5 Hz, P=.02) and fractal dimension of RR time series (P=.03). QTvi, a measure of QT interval variability, increased in the pemoline group (P=.05). CONCLUSION: Pemoline, but not fluoxetine, decreases heart period variability (HPV) in the HF power, suggesting a vagolytic effect on cardiac autonomic function. Pemoline is also associated with an increase in QT interval variability, a measure that is sensitive to adrenergic agonists.

Adult↗
PubMed2000

Altered baroreflex responses in alpha7 deficient mice.

The autonomic nervous system controls and coordinates several cardiovascular functions, including heart rate, arterial pressure, blood flow and vasomotor tone. Neuronal nicotinic acetylcholine receptors (nAChRs) are the interface between the nervous system and the cardiovascular system, but it is not known which nAChR subtypes regulate autonomic function in vivo. Nicotinic AChRs containing the alpha7 subunit are a candidate subtype in autonomic ganglia. Stimulation of these nAChRs can increase neurotransmitter release via presynaptic mechanisms, as well as mediate fast synaptic transmission via postsynaptic mechanisms. To investigate the role of the alpha7 nAChR subunit in cardiac autonomic function, we measured baroreflex-mediated responses in alpha7 null mice. Here we show that the alpha7 null mice have impaired sympathetic responses to vasodilatation, as sodium nitroprusside infusion triggered a 48% heart rate increase in wild type mice but only a 21% increase in the alpha7 nulls (P < 0.001). The mutant mice developed supersensitivity to adrenergic agonists, although norepinephrine release from sympathetic nerve terminals could be elicited through mechanisms alternative to nAChR stimulation. Baroreflex-mediated parasympathetic responses were normal in alpha7 null mice. The decreased baroreflex-mediated tachycardia in alpha7 mutant mice indicates that alpha7-containing nAChRs participate in the autonomic reflex that maintains blood pressure homeostasis. The alpha7 mutant mice may serve as a model of baroreflex impairment arising from autonomic dysfunction.

Animals↗
PubMed2001

Heart rate and QT variability in children with anxiety disorders: a preliminary report.

This study compared beat-to-beat heart rate and QT variability in children with anxiety disorders (n = 7) and normal controls (n = 15) by using an automated algorithm to compute QT intervals. An increase in QT variability appears to be associated with a higher risk for sudden cardiac death. A decrease in heart rate variability is also linked to significant cardiovascular events. Supine detrended QT variability, QT variability corrected for mean QT interval, and QTvi (a log ratio of QT variance normalized for mean QT over heart rate variability normalized for mean heart rate) were significantly higher in children with anxiety compared to controls (P < 0.05). The largest Lyapunov Exponent (LLE) of heart rate time series was significantly lower (P < 0.05) in children with anxiety compared to controls. These findings suggest a relative increase in sympathetic activity and a relative decrease in cardiac vagal activity in children with anxiety disorders, and are discussed in the context of the effects of tricyclics on cardiac autonomic function in children, and the rare occurrence of sudden death during tricyclic antidepressant treatment.

Antidepressive Agents, Tricyclic↗
PubMedDate not supplied

Autonomic nerve affection in leprosy.

Leprosy has been shown to affect almost all systems of human body and abnormalities in functions of autonomic nerves innervating various parts have been observed in several studies. In the skin and its appendages, the common changes are anhidrosis and varying degree of impaired sweat response. Signs of denervation of iris and reduced intraocular pressure are permanent features of autonomic involvement in the eye. In the cardiac autonomic functions, rhythm disturbances have been documented by several investigators. Respiratory function test studies have shown impaired breath holding time and decreased response to cough as well as other changes indicating blockade of vagus nerves and sympathetic plexus. Abnormal testicular pain sensation and diminished nocturnal penile tumiscence provide evidence of afflication of autonomic nerves of male genital system. Other important autonomic nervous system involvements include the nerves innervating the capillaries of legs. These changes have been observed to be more in extensive and long standing disease which indicate the need to study all these aspects in prospective studies specially in the light of early institution of multidrug treatment.

Autonomic Pathways↗
PubMed1995

Heart rate and blood pressure variability: implications for psychiatric research.

Symptoms of anxiety suggest autonomic dysfunction and most of the psychotropic agents used to treat anxiety and affective disorders have strong autonomic effects. This article describes the utility and importance of analysis of heart rate and blood pressure time series to study cardiac autonomic function in psychiatric research. The variability of heart rate between 0.15 and 0.5 Hz is related to respiratory sinus arrhythmia, and is modulated by cholinergic activity in both supine and standing postures, while the variability between 0.04 and 0.15 Hz is dually influenced by cholinergic and adrenergic mechanisms which can be used as a relative measure of sympathetic activity in standing posture. Analysis of beat-to-beat control of heart rate and blood pressure gives important information about cardiac sympathetic and parasympathetic interaction, which could be used to study the possible link between anxiety and depressive disorders and increased cardiovascular morbidity.

Autonomic Nervous System↗
PubMed2004

Differences in heart rate turbulence between patients with coronary artery disease and patients with ventricular arrhythmias but structurally normal hearts.

The term "heart rate turbulence" (HRT) indicates the physiologic changes in the sinus cycle that follow a ventricular premature complex; impaired HRT denotes abnormalities in cardiac autonomic function. To investigate whether HRT is impaired in patients with stable coronary artery disease (CAD), we studied 29 patients with documented CAD and frequent (>/=30/hour) ventricular premature complexes on Holter monitoring and 31 patients with frequent ventricular arrhythmias but normal hearts (NH-VA). HRT and heart rate variability analyses were analyzed on 24-hour Holter recordings. HRT variables differed significantly between the 2 groups (turbulence onset -0.20 +/- 1.7% vs -0.67 +/- 2.2%, p = 0.00001; turbulence slope 2.83 +/- 1.9 vs 10.83 +/- 7.4 ms/RR, p = 0.0001 in patients with CAD and NH-VA, respectively). The difference was independent of a history of previous myocardial infarction, left ventricular function, and age. Top quartile turbulence onset values (>-0.26%) and bottom quartile turbulence slope values (<2.12 ms/RR) had similar predictive power in discriminating between patients with CAD and NH-VA (positive predictive value 86.7%, negative predictive value 64.4% for both). Among heart rate variables, bottom quartile SD of all RR intervals values (<96.3 ms) only had the same power of HRT variables in discriminating between patients with CAD and NH-VA. Thus, our data show that HRT variables are impaired in patients with CAD patients versus those with NH-VA, indicating abnormalities in the control of short-term cardiac autonomic mechanisms resulting in decreased vagal activity with likely predominant sympathetic activity.

Adult↗
PubMed2000

What do epidemiologic findings tell us about health effects of environmental aerosols?

In the last 10 years there has been an abundance of new epidemiological studies on health effects of particulate air pollution. The overall evidence suggests that fine particulate pollution can be an important risk factor for cardiopulmonary disease. Long-term, repeated exposure to fine particulate air pollution may increase the risk of chronic respiratory disease and the risk of cardiopulmonary mortality. Short-term exposures exacerbate existing cardiovascular and pulmonary disease and increase the risk of becoming symptomatic, requiring medical attention, or even dying. This paper outlines the results of the basic epidemiologic studies and briefly reviews and discusses recent studies that have looked at specific physiologic health endpoints in addition to lung function. A few recent, mostly exploratory pilot studies, have observed particulate pollution associations with blood plasma viscosity, heart rate, heart rate variability, and indicators of bone marrow stimulation. A systemic response to particulate-related pulmonary inflammation remains somewhat speculative. The epidemiologic evidence, nevertheless, seems consistent with the hypothesis that particle-induced pulmonary inflammation, cytokine release, and altered cardiac autonomic function may be part of the pathophysiological mechanisms or pathways linking particulate pollution with cardiopulmonary disease.

Aerosols↗
PubMed1998

Clinical trials for polyneuropathy: the role of nerve conduction studies, quantitative sensory testing, and autonomic function testing.

Clinical trials to assess the treatment of diabetic and other forms of polyneuropathy are becoming increasingly common. Nerve conduction studies, quantitative sensory testing, and autonomic function testing are often used in these trials. This article reviews the sensitivity and reproducibility of these measures to detect change in peripheral nerve function during long-term trials. The attributes of nerve conduction studies that are likely to be most useful are summated or averaged sensory nerve action potential amplitudes and averaged motor nerve conduction velocities. Summated or averaged compound muscle action potential amplitude and mean F-wave latencies are also highly informative. Vibratory detection thresholds are sensitive, specific, and highly reproducible for assessment of large myelinated sensory fibers, with cooling and warming detection thresholds also having good sensitivity for small myelinated sensory fibers. Although less well validated for longitudinal trials, visual analogue scale scoring of heat pain provides assessment of unmyelinated sensory fibers. Heart rate variation to deep breathing, Valsalva, or standing are useful to assess cardiac autonomic function. Based on these data that are reviewed and consistent with the conclusions of previous consensus conferences, a combination of these studies is recommended.

Autonomic Nervous System↗
PubMed2001

Presence of a pet dog and human cardiovascular responses to mild mental stress.

The mechanisms underlying the possible cardiovascular benefits of pet ownership have not been established. Using a randomized design, the effect of a friendly dog on cardiovascular and autonomic responses to acute, mild mental stress was investigated. Seventy-two subjects (aged 40 +/- 14 y; mean +/- SD) participated. Rest was alternated with mental stress during four 10-minute periods. An unknown dog was randomly selected to be present during the first or the second half of the study. Blood pressure (BP) and heart rate (HR) were monitored continuously and cardiac autonomic function assessed using spectral analysis of heart period. Heart period variability data were expressed as the ratio of 0.1 Hz to respiratory or high frequency variation (LF/HF). Whereas mental stress significantly increased BP and HR in the absence of the dog (from 125/71 +/- 3/2 to 133/75 +/- 3/2 mm Hg; p <0.001), the presence of the dog had no effect on these variables. Heart period LF/HF ratio was lowest in dog owners in the presence of the dog (dog present 2.8 +/- 0.3 versus dog absent 3.4 +/- 0.4; p <0.001) and in non-dog owners in the absence of the dog (dog present 3.4 +/- 0.4 versus dog absent 2.8 +/- 0.3; p <0.001). In conclusion, a friendly but unfamiliar dog does not influence BP or HR either at rest or during mild mental stress. Cardiac autonomic profile was most favorable in the presence of the dog for dog owners and in the absence of the dog for non-owners.

Adult↗