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Results 701 - 750 of 1331
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Uberfuhr P - - 2000
BACKGROUND: Orthotopic heart transplantation (HTx) results in complete cardiac denervation. Reestablished partial sympathetic nerve function has been found in patients some years after HTx. However, the atrial and ventricular regional patterns of reinnervation have not been established. METHODS: Two parallel methods were used to evaluate the regional restoration of sympathetic ...
Palomba D - - 2000
The autonomic basis of cardiac reactions to unpleasant film stimuli was investigated. Film clips depicting major surgery, threats of violence, and neutral material were presented to 46 subjects. Self-report measures of emotion were obtained, as well as heart rate, respiration rate, respiratory sinus arrhythmia, T-wave amplitude and skin conductance level. ...
Tjeerdsma G - - 2000
BACKGROUND: Mibefradil was recently withdrawn from the market because of an unfavorable clinical profile in patients with chronic heart failure. Although drug interactions appear to play a role, other mechanisms such as proarrhythmia and autonomic deterioration could also be relevant. Chronic heart failure is accompanied by autonomic impairment and analysis ...
Stein P K - - 2000
BACKGROUND: Clinical and demographic determinants of heart rate variability (HRV), an almost universal predictor of increased mortality, have not been systematically investigated in patients post myocardial infarction (MI). HYPOTHESIS: The study was undertaken to evaluate the relationship between pretreatment clinical and demographic variables and HRV in the Cardiac Arrhythmia Suppression ...
Esler M - - 2000
Recent demonstration that the level of sympathetic nervous drive to the failing heart in patients with severe heart failure is a major determinant of prognosis, and that mortality in heart failure is reduced by beta-adrenergic blockade, indicate the clinical relevance of heart failure neuroscience research. The cardiac sympathetic nerves are ...
Patel K P - - 2000
A number of neurohumoral processes are activated in heart failure, including an increase in the plasma concentration of norepinephrine. Few studies have been performed to examine the role of the central nervous system in the activation of sympathetic outflow during heart failure (HF). In this paper I review these limited ...
Biswas P K - - 2000
Chronic heart failure is associated with excessive neurohormonal activation. Analysis of heart rate variability is considered a valid technique for assessment of the autonomic balance of the heart. Twenty symptomatic patients of dilated cardiomyopathy in NYHA class II-IV symptomatic status and as many normal controls were subjected to 24 hours ...
Lanza G A - - 2000
BACKGROUND: We have recently demonstrated a striking impairment in cardiac uptake of 123I-metaiodobenzylguanidine (MIBG) in most patients with syndrome X. In this study we investigated the relationship between cardiac MIBG defects and cardiac autonomic activity in these patients. METHODS: MIBG myocardial scintigraphy and time-domain and frequency-domain heart rate variability (HRV) ...
Inazumi T - - 2000
Although the autonomic nervous system has been implicated in the genesis of coronary spasm, the precise mechanism by which it serves as the trigger of coronary spasm remains unclear. The aim of this study was to investigate changes in autonomic nervous activity associated with ischemic episodes in patients with variant ...
Wang W - - 2000
Heart failure is characterized by an elevation in sympathetic tone. The mechanisms responsible for this sympatho-excitation of heart failure are not completely understood. Several studies from this laboratory have compared differences in the cardiac "sympathetic afferent" reflex between sham dogs and dogs with pacing-induced heart failure. We found 1) that ...
Wennerblom B - - 2000
AIM: To investigate whether uncomplicated chronic coronary artery disease causes changes in heart rate variability and if so, whether the heart rate variability pattern is different from that described in patients with acute myocardial infarction. METHODS: Heart rate variability was studied in 65 patients with angina who had no previous ...
Clark A L - - 2000
Chronic heart failure is characterised by excess adrenergic activity that augurs a poor prognosis. The reasons for increased adrenergic activity are complex and incompletely understood. The circumstantial evidence relating increased activity to adverse outcome is powerful, but not yet conclusive. In normal subjects, autonomic control of the circulation is predominantly ...
Davila D F - - 2000
Cardiac chambers have afferent connections to the brainstem and to the spinal cord. Vagal afferents mediate depressor responses and become activated by volume expansion, increased myocardial contractility and atrial natriuretic factor. Sympathetic afferents, on the contrary, are activated by metabolic mediators, myocardial ischemia and cardiac enlargement. These opposite behaviors may ...
Yi G - - 2000
Heart rate variability (HRV) analysis from 24-hour ambulatory ECG has been widely used in risk stratification of patients after myocardial infarction (MI). The accuracy of HRV assessment is known to potentially vary when different commercial systems are used. However, the consistency of HRV measurements has never been fully investigated. Twenty-six ...
Halberg Franz - - 2000
Magnetic storms trigger myocardial infarctions with mechanisms relating to heart rate variability. Solar cycle-to-solar cycle differences and solar cycle stage dependence shown herein may resolve prior controversy and serve to advocate coordinated worldwide systematically aligned biological and physical monitoring. * This paper was originally invited by the historian-geophysicist Wilfried SCHRöDER ...
Machado C R - - 2000
Congestive heart failure (CHF) is associated with activation of the cardiac sympathetic nerves. However, impairment of the sympathetic nerve terminals in patients with CHF has been indicated by studies showing reduction of cardiac norepinephrine uptake and stores. This investigation studies the histochemical evaluation of the sympathetic nerve terminals in CHF. ...
La Rovere M T - - 2000
As the arterial baroreflex importantly contributes to modulation of the autonomic influences on the heart and thereby arrhythmogenesis, baroreflex sensitivity has been used as a measure of the interaction between sympathetic and parasympathetic activities at the cardiac level. The most widely applied technique both in the experimental and clinical setting ...
Soejima K - - 2000
The age-adjusted, heart rate variability (HRV) was evaluated as a parameter for the severity of heart failure and its prognosis. HRV was obtained by 24-h Holter monitoring in patients with left ventricular dysfunction (LVD). New York Heart Association (NYHA) functional classification, echocardiography, radioisotope ventriculography, and blood examination were performed, and ...
Tokudome T - - 1999
The purpose of this study was to assess the role of the autonomic nervous system in the regulation of basal coronary artery tone in normal and atherosclerotic plaque segments by using intravascular ultrasound in humans. In each of 21 patients, a short-axis image at one site of coronary artery was ...
Joho S - - 1999
OBJECTIVES: We assessed time-varying spectral components of heart rate and left ventricular (LV) pressure variability during coronary angioplasty to elucidate dynamic autonomic responses to transient myocardial ischemia. BACKGROUND: Sympathoexcitatory reflexes elicited by acute coronary occlusion are rarely addressed in the clinical settings because of a lack of technique to monitor ...
Butera G - - 1999
AIM: To determine whether cavopulmonary connections are associated with abnormalities of heart rate variability. METHODS: Heart rate variability was studied by 24 hour Holter monitoring in 39 patients (mean (SD) age 12.2 (4.1) years) who underwent cavopulmonary connection operations (partial in 12, total in 13, and atriopulmonary in 14). Two ...
Mani V - - 1999
INTRODUCTION: Short-term heart rate variability (HRV) may change immediately before onset of a ventricular arrhythmia (ONSET). METHODS AND RESULTS: Power spectrum analysis was performed on instantaneous heart rate (IHR; including all beats) and normal heart rate (NHR; excluding ectopics) curves obtained at equally spaced 0.5-second intervals using a cubic spline. ...
Kontopoulos A G - - 1999
Abnormal autonomic nervous system impairment in patients with acute myocardial infarction (AMI) has a circadian pattern with the greatest manifestation in the morning hours; it probably plays an important role in the pathogenesis of cardiac arrhythmias and acute ischemic syndromes. Angiotensin-converting enzyme inhibitors improve autonomic function in patients with AMI, ...
Castellanos A - - 1999
This study revealed that conventional temporal and spectral indexes of heart rate variability were reduced in patients with sinus tachycardia due to various, easily detectable, causes. These findings were attributed to the fast rates, per se, regardless of the cause, without reflecting a particular shift in the degree of autonomic ...
Vaile J C - - 1999
Evidence from animal studies suggests that beta-blockers can act within the central nervous system to increase cardiac vagal motoneuron activity. We have attempted to determine whether such an effect is evident in healthy humans, by examining the effects of lipophilic and hydrophilic agents on heart rate variability and cardiac vagal ...
Crick S J - - 1999
The immunological problems of pig hearts supporting life in human recipients have potentially been solved by transgenic technology. Nevertheless, other problems still remain. Autonomic innervation is important for the control of cardiac dynamics and there is evidence suggesting that some neurons remain intact after transplantation. Previous studies in the human ...
Brembilla-Perrot B - - 1999
AIM: To find a rapid way of identifying non-responders to D, L-sotalol in patients with ventricular tachycardia. METHODS: Programmed ventricular stimulation and RR variability were studied in the control state and 10 days after treatment with 160 to 320 mg of D,L-sotalol in 36 consecutive patients with ventricular tachycardia. RESULTS: ...
Rasmussen K G - - 1999
Anticholinergic medications such as atropine or glycopyrrolate have long been used in electroconvulsive therapy (ECT) to eliminate parasympathetically mediated dysrhythmias. However, such agents increase heart rate and myocardial workload and may increase risk of cardiac adverse events. What is needed is an intervention that is parasympatholytic without substantially increasing myocardial ...
Matheja P - - 1999
The autonomic innervation of the heart modifies most cardiac functions. Especially the heart rate and the force of contraction of myocytes are modulated by the autonomic nervous system. A number of specific neurotransmitters interact with receptors on post- and presynaptic binding sites regulating the complex electromechanical system of the heart. ...
Du X J - - 1999
OBJECTIVE: To seek direct evidence for a cause-effect relation between sympathetic activation and arrhythmogenesis. METHODS: Rats underwent open-chest surgery with either coronary artery occlusion or sham operation, and were studied 8 weeks later using in situ heart perfusion and nerve stimulation methods. RESULTS: Infarcted rats showed cardiac functional impairment and ...
West B J - - 1999
Human heart rate, controlled by complex feedback mechanisms, is a vital index of systematic circulation. However, it has been shown that beat-to-beat values of heart rate fluctuate continually over a wide range of time scales. Herein we use the relative dispersion, the ratio of the standard deviation to the mean, ...
Storella R J - - 1999
OBJECTIVE: To determine whether there are differences among measures of heart rate variability (HRV; traditional and nonlinear) after anesthesia and cardiac surgery. DESIGN: Prospective. SETTING: University hospital. PARTICIPANTS: Patients scheduled for cardiac surgery. INTERVENTIONS: None. Medical management was not varied as part of this study. MEASUREMENTS AND MAIN RESULTS: HRV ...
Porta A - - 1999
A method that enables measurement of the degree of coupling between two signals is presented. The method is based on the definition of an uncoupling function calculating, by means of entropy rates, the minimum amount of independent information (i.e. the information carried by one signal which cannot be derived from ...
Wang W - - 1999
A previous study from this laboratory has shown that cardiac sympathetic afferent stimulation by epicardial application of bradykinin (BK) and capsaicin was significantly enhanced in the dog with experimental heart failure (HF). The present study determined whether activity from cardiac sympathetic chemosensitive afferent endings is enhanced in HF. Rapid ventricular ...
Bonaduce D - - 1999
BACKGROUND: Decreased heart rate variability (HRV), indicating derangement in cardiac autonomic control, has been reported in patients with chronic heart failure. However, the independent and incremental prognostic value of HRV over clinical data and measures of left ventricular dysfunction has been less thoroughly investigated. This study was designed to evaluate ...
Maini C L - - 1999
Marked changes in cardiac function have been noted in patients with hyperthyroidism or hypothyroidism due both to changes in sympathetic system function and to biochemical modifications of myocardial tissue. Metaiodobenzylguanidine (MIBG), an analogue of norepinephrine, can be used to evaluate myocardial sympathetic tone. Here, we report myocardial 123I-MIBG kinetics in ...
Pan H L - - 1999
1. Chest pain caused by myocardial ischaemia is mediated by cardiac sympathetic afferents. The mechanisms of activation of cardiac afferents during ischaemia remain poorly understood. Increased lactic acid production is associated closely with myocardial ischaemia. The present study examined the role of protons generated during ischaemia in activation of cardiac ...
Azevedo E R - - 1999
BACKGROUND: Muscarinic receptors on adrenergic nerve terminals attenuate norepinephrine release. The role of these receptors in the modulation of cardiac norepinephrine release in humans remains uncertain. METHODS AND RESULTS: Twelve patients with normal left ventricular (LV) function and 18 with congestive heart failure (CHF) were studied. A radiotracer technique was ...
Hedman A E - - 1999
The new finding was that mean heart rate and heart rate variability were more closely coupled in patients with more advanced LV dysfunction. Mean heart rate explained a larger portion of variance in heart rate variability in patients in the lowest LVEF quartile than in those in the highest one. ...
Katz A - - 1999
BACKGROUND: We evaluate a simple, bedside test that measures 1-minute heart rate variability in deep breathing as a predictor of death after myocardial infarction. METHODS: Bedside heart rate variability was assessed in 185 consecutive patients 5.1 +/- 2.5 days after a first myocardial infarction. Patients were instructed to take 6 ...
Tokgözoglu S L - - 1999
BACKGROUND AND PURPOSE: Stroke has been shown to alter autonomic function. The purpose of this study was to show the differential effects of stroke localization on autonomic function parameters assessed by heart rate variability (HRV). METHODS: To determine the differential effect of ischemic stroke localization on autonomic cardiac innervation, we ...
Nishiue T - - 1999
To assess clinically whether alterations of autonomic tone precede left ventricular dilatation, heart rate variability and early left ventricular dilatation after a first myocardial infarction were assessed. Low-frequency power (LF), high-frequency power (HF), and total power (TP) were obtained by ambulatory electrocardiogram on day 1 in 53 patients with a ...
Silke B - - 1999
Full antagonists of the cardiac beta-adrenoceptor improve heart-rate variability (HRV) in humans; however, partial agonism at the beta2-adrenoceptor has been suggested to decrease HRV. We therefore studied the HRV effects of some partial agonists of the beta1- and beta2-adrenoceptors in normal volunteers. Under double-blind and randomised conditions (Latin square design), ...
Pluim B M - - 1999
OBJECTIVE: To examine the correlation between heart rate variability and left ventricular mass in cyclists with an athlete's heart. METHODS: Left ventricular mass and diastolic function were determined at rest and myocardial high energy phosphates were quantified at rest and during atropine-dobutamine stress in 12 male cyclists and 10 control ...
Nishinaka T - - 1999
We investigated the changes in cardiac autonomic nervous activities during long-term nonpulsatile left heart bypass (NLHB) by analyzing heart rate variability. A pulsatile ventricular assist device was installed in 3 goats, and pulsatile left heart bypass (PLHB) was conducted for 2 weeks. Then, NLHB was maintained for the following 4 ...
Bengel F M - - 1999
Metaiodobenzylguanidine (MIBG) washout from the myocardium has been thought to reflect sympathetic nerve tone. After acute myocardial infarction, however, little is known about this parameter. The aim of this study was to determine the significance of cardiac washout after myocardial infarction and early reperfusion by investigating MIBG kinetics and correlating ...
Notarius C F - - 1999
The concept that spectral analysis of heart rate variability (HRV) can estimate cardiac sympathetic nerve traffic in subjects with both normal and impaired left ventricular systolic function has not been validated against muscle sympathetic nerve activity (MSNA). We used coarse-graining spectral analysis to quantify the harmonic and non-harmonic, or fractal, ...
McLeod K A - - 1999
OBJECTIVE: To examine autonomic function as assessed by heart rate variability in patients 10 or more years after repair of tetralogy of Fallot, and to relate this to cardiac structure, function, and electrocardiographic indices. METHODS: Heart rate variability was measured by standard time domain techniques on a 24 hour Holter ...
Delamont R S - - 1999
In previous studies of the relationship between the cardiac autonomic activity and seizures, assessment of autonomic changes has relied on alterations in heart rate or R-R intervals. We have used a recently developed continuous index of cardiac parasympathetic activity (CIPA) to examine 20 seizures in 10 patients during pre-surgical evaluation ...
Lotze U - - 1999
In patients with idiopathic dilated cardiomyopathy (IDC) the increased sympathetic activity owing to chronic congestive heart failure leads to an imbalance of cardiac autonomic tone, as reflected by decreased heart rate variability (HRV). Iodine-123-metaiodobenzylguanidine (123-I-MIBG), which has the same affinity for sympathetic nerve endings as norepinephrine, can be used to ...
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