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Results 701 - 750 of 1300
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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 ...
Druschky K - - 1999
We investigated cardiac sympathetic innervation by metaiodobenzylguanidine (MIBG) imaging in a patient with tonic pupils, loss of tendon reflexes, and segmental anhidrosis (Ross syndrome). Despite normal cardiovascular reflex tests, we observed a reduced global myocardial MIBG uptake as well as a regional uptake defect over the posterolateral cardiac territory indicating ...
Sapoznikov D - - 1999
Changes in heart rate preceding ventricular ectopic beats may be used to identify clinical subsets of patients. We evaluated RR interval patterns preceding ventricular ectopic beats with a rate enhancement method which estimates ventricular ectopic beat dependence on the sinus RR interval preceding the ventricular ectopic beat and the dynamic ...
Kaye D M - - 1999
OBJECTIVES: The aim of the present study was to evaluate the influence of amiodarone on neurochemical parameters of sympathetic nervous activity in patients with congestive heart failure. BACKGROUND: Unlike most antiarrhythmic agents, amiodarone has been shown to exert a beneficial effect on survival in some studies of patients with congestive ...
Fallen E L - - 1999
BACKGROUND: The implication of an arrhythmogenic role for infarction-induced disruption of regional myocardial sympathetic nerve activity has led to a search for noninvasive methods to study regional sympathetic nerve activity in patients after infarction. METHODS AND RESULTS: By using positron emission tomography, we measured the time course of myocardial hypoperfusion ...
Yoshikawa T - - 1999
BACKGROUND: The clinical significance of the determination of heart rate variability and baroreceptor sensitivity relating to cardiac function and neurohumoral factors remains to be established. METHODS AND RESULTS: We investigated the relation between conventional clinical variables and frequency domain analysis of heart rate variability and baroreceptor sensitivity in 146 patients ...
Airaksinen K E - - 1999
Experimental studies suggest that autonomic mechanisms are important in the genesis of ischemia-induced malignant ventricular arrhythmias, but the role of the autonomic nervous system in human arrhythmogenesis is not well known. To assess whether heart rate variability (HRV) predicts the occurrence of ventricular arrhythmias during acute coronary artery occlusion, we ...
Lin J L - - 1999
BACKGROUND: beta-Blocker therapy is believed to modulate the detrimental effect of overcompensating neurohormonal activation in chronic heart failure. However, clinical doubts remain, particularly the physiologic sympathovagal balance. METHODS: To respond to clinical concern about worsening autonomic nervous perturbation in beta-blocker therapy of advanced congestive heart failure, 15 consecutive patients were ...
Uehara A - - 1999
BACKGROUND: Diabetic cardiac autonomic dysfunction often causes lethal arrhythmia and sudden cardiac death. 123I-Metaiodobenzylguanidine (MIBG) can evaluate cardiac sympathetic dysfunction, and analysis of heart rate variability (HRV) can reflect cardiac parasympathetic activity. We examined whether cardiac parasympathetic dysfunction assessed by HRV may correlate with sympathetic dysfunction assessed by MIBG in ...
Delahaye N - - 1999
Familial amyloid polyneuropathy (FAP) is a rare and severe hereditary form of amyloidosis, due to nervous deposits of a genetic variant transthyretin produced by the liver and characterized by both sensorimotor and autonomic neuropathy. Left ventricular systolic dysfunction is rare, but conduction disturbances and sudden deaths can occur. The neurological ...
Lanfranchi P A - - 1999
BACKGROUND: Nocturnal Cheyne-Stokes respiration (CSR) occurs frequently in patients with chronic heart failure (CHF), and it may be associated with sympathetic activation. The aim of the present study was to evaluate whether CSR could affect prognosis in patients with CHF. METHODS AND RESULTS: Sixty-two CHF patients with left ventricular ejection ...
Zhuang Z P - - 1999
Radioactive-iodine-labeled meta-iodobenzylguanidine (MIBG) is currently being used as an in vivo imaging agent to evaluate neuroendocrine tumors as well as the myocardial sympathetic nervous system in patients with myocardial infarct and cardiomyopathy. It is generally accepted that MIBG is an analogue of norepinephrine and its uptake in the heart corresponds ...
Azuaje F - - 1999
Coronary heart disease is a multifactorial disease and it remains the most common cause of death in many countries. Heart rate variability has been used for non-invasive measurement of parasympathetic activity and prediction of cardiac death. Patterns of heart rate variability associated with respiratory sinus arrhythmia have recently been considered ...
Lanza G A - - 1999
The aim of this study was to investigate the usefulness of heart rate variability (HRV) in predicting cardiac mortality in patients with a recent acute myocardial infarction at high risk of events. Time- and frequency-domain HRV was assessed on 24-hour pre-discharge Holter recording of 81 patients (mean age 65 +/- ...
Petretta M - - 1999
BACKGROUND: Analysis of heart rate variability (HRV) is a valuable noninvasive method for quantifying autonomic cardiac control in humans and has been utilized during dipyridamole echocardiographic test to differentiate positive from negative test results. HYPOTHESIS: We aimed to evaluate, by means of HRV analysis, the influence of the angiographic severity ...
Hartmann F - - 1999
OBJECTIVE: To assess presynaptic function of cardiac autonomic innervation in patients with advanced congestive heart failure using positron emission tomography (PET) and the recently developed radiolabelled catecholamine analogue carbon-11 hydroxyephedrine (HED) as a marker for neuronal catecholamine uptake function. DESIGN AND PATIENTS: 29 patients suffering from dilated cardiomyopathy with moderate ...
Tygesen H - - 1999
Beta-Blockers reduce mortality in patients with congestive heart failure and a proposed mechanism has been changes of autonomic tone. Heart rate variability is a non-invasive tool to estimate cardiac autonomic tone. The aim was to study changes of heart rate variability in patients with congestive heart failure on placebo, on ...
Weber F - - 1999
AIMS: Determination of the influence of therapy with bisoprolol and nifedipine on the heart rate variability of patients from the Total Ischemic Burden Bisoprolol Study and examination of the prognostic value. METHODS AND RESULTS: Four hundred and twenty-two patients with stable angina were included. The heart rate variability was determined ...
Stein P K - - 1999
Indices of heart rate variability (HRV) provide a window onto autonomic modulation of the heart. HRV indices, determined in either the time or frequency domain, are closely related and reflect parasympathetic, mixed sympathetic, and parasympathetic and circadian rhythms. In population studies, decreased HRV has had predictive value for mortality among ...
Kerut E K - - 1999
Analysis of heart rate variability (HRV) permits an assessment of sympathetic and parasympathetic activity from EKG recordings. Analysis of HRV may be performed in both the time and frequency domain by the application of mathematical principles of signal processing. HRV demonstrates abnormalities in myocardial infarction, sudden death, heart failure, autonomic ...
Dreiseitl S - - 1999
This paper evaluates the variable selection performed by several machine-learning techniques on a myocardial infarction data set. The focus of this work is to determine which of 43 input variables are considered relevant for prediction of myocardial infarction. The algorithms investigated were logistic regression (with stepwise, forward, and backward selection), ...
Del Greco M - - 1999
ST-elevation acute myocardial ischemia occurred after phenylephrine infusion in a patient with severe coronary artery disease and recent myocardial infarction. The subsequent administration of nitroglycerin led to a vasovagal response with symptomatic hypotension and bradycardia. During myocardial ischemia, heart-rate variability and baroreflex sensitivity analysis described a marked activation of sympathetic ...
Lanza G A - - 1998
A low heart rate variability (HRV) has been shown to be a powerful predictor of cardiac events in patients surviving an acute myocardial infarction (MI), but it is not clear yet which among the HRV parameters has the best predictive value. Time domain and frequency domain HRV was assessed on ...
Napier L D - - 1998
The vagotonic effect of chronic morphine on the parasympathetic control of the heart was examined in dogs treated with morphine for 2 wk. Because normal vagal function is critical to myocardial stability, the study was conducted to evaluate for potential impairments following chronic vagal stimulation. The hypothesis that persistent vagal ...
Scalvini S - - 1998
Autonomic dysfunction seems to be involved in the progression and prognosis of congestive heart failure. Measurement of heart rate variability (HRV) provides a noninvasive method to obtain reliable and reproducible information on autonomic modulation of heart rate, but there is a difficulty in using HRV as a quantitative estimate of ...
Calvert C A - - 1998
Heart rate variability (HRV), usually performed from 24 hour ambulatory ECG recordings, measures the variability of the heart rate. Alterations in autonomic balance and baroreceptor function, increased plasma norepinephrine levels, and reduced HRV have been associated with progressive myocardial failure. Not only has reduced HRV been associated with the degree ...
Láng E - - 1998
The purpose of this study was to contribute to the improvement of stratification of post-myocardial infarction patients at increased risk of malignant ventricular arrhythmia (MVA). Power spectral analysis of heart period variability (HPV) was used as a non-invasive tool to assess cardiac autonomic control. Three groups were used: (1) post-myocardial ...
Nolan J J General Infirmary and St James's University Hospital, Leeds, - - 1998
Patients with chronic heart failure (CHF) have a continuing high mortality. Autonomic dysfunction may play an important role in the pathophysiology of cardiac death in CHF. UK-HEART examined the value of heart rate variability (HRV) measures as independent predictors of death in CHF. In a prospective study powered for mortality, ...
Fauchier L - - 1998
Heart rate variability is a noninvasive indicator of autonomic nervous system activity. The role of the autonomic nervous system in the genesis of atrial or ventricular arrhythmias is now well established. Little is known about the effects of flecainide on heart rate variability in patients with normal heart structure, the ...
Kurata C - - 1998
It is assumed that the low-frequency power (LF) of heart rate variability (HRV) increases with progress of congestive heart failure (CHF), therefore positively correlating with cardiac 123I-metaiodobenzylguanidine (MIBG) washout. It is demonstrated here that HRV, including normalized LF, correlated inversely with MIBG washout and positively with the ratio of heart-to-mediastinum ...
Wittling W - - 1998
Hemisphere asymmetry in sympathetic control of myocardial performance was studied in healthy human subjects using lateralized film presentation for selective sensory stimulation of the hemispheres and impedance cardiography for the evaluation of cardiac output, systolic time intervals and myocardial contractility. Results revealed a clear and consistent right hemisphere predominance in ...
Stys A - - 1998
Heart rate variability (HRV) has become a popular method for the studies of physiologic mechanisms responsible for the control of heart rate fluctuations, in which the autonomic nervous system appears to play a primary role. Depression of HRV has been observed in many clinical scenarios, including autonomic neuropathy, heart transplantation, ...
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