Search Results
Results 251 - 300 of 1133
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Roldán Vanessa - - 2003
BACKGROUND: A prothrombotic or hypercoagulable state has been described in AF, which could increase the risk of thromboembolism. As inflammation has been related to thrombogenesis and endothelial activation, we hypothesised that the prothrombotic state in AF (as assessed by an index of thrombogenesis, prothrombin fragment 1+2 [F1+2]) and endothelial activation ...
Amitzur Giora - - 2003
PURPOSE: To study refractoriness and conduction interaction during modulation of non-ischemic ventricular fibrillation (VF) by flecainide. METHODS: Isolated feline and rabbit hearts were used. (a) In the feline hearts (n = 8), electrophysiological parameters were measured before and after flecainide administration (0.6, 1.2 x 10(-6) M). During pacing the parameters ...
Yoshiga Yasuhiro - - 2003
The aims of this study were to evaluate the changes in the electrophysiological characteristics of the right atrium after the administration of flecainide and to clarify whether flecainide has a selective effect on human atrial tissue. Electrophysiological measurements were made in 38 patients, before and after intravenous administration of flecainide ...
Malfatto G - - 2003
AIMS: Repolarization has rate-dependent and rate-independent components. A function considering such components separately was validated in canine Purkinje fibres and applied to the QT/RR relation in humans. METHODS AND RESULTS: Action potential duration (APD) was measured in Purkinje fibres during steady-state pacing at different cycle lengths (CL) and after prolonged ...
Cools F J C - - 2003
AIMS: The presence of far field R wave sensing (FFRS) is usually evaluated in patients with dual chamber pacemakers in supine position. To check if this approach is valid, we tested whether FFRS is consistent both in terms of amplitude threshold and timing characteristics in different daily life conditions. METHODS ...
Greco Enrico Maria - - 2003
An innovative control parameter for rate responsive (RR) pacing that uses a sensor to measure mechanical vibrations generated by the myocardium during the isovolumetric contraction phase (peak endocardial acceleration [PEA]), has been devised by SORIN Biomedica (BEST Living System). To assess the physiological sensitivity of the pacemaker sensor along with ...
Fabritz Larissa - - 2003
It has been suggested that both pacing and treatment with mexiletine may reduce torsade de pointes (TdP) arrhythmias in patients with long QT syndrome 3 (LQT3), but it is not fully understood how these interventions could prevent TdP. We therefore studied the effects of pacing and mexiletine in mice with ...
Nielsen Jens Cosedis - - 2003
Biventricular (BiV) pacing has been found to improve systolic function and exercise tolerance in patients with severe congestive heart failure and bundle branch block. The mechanisms behind this beneficial effect is still not sufficiently clarified. To evaluate the regional myocardial perfusion (MP) during BiV pacing and after acute change of ...
Duncan A - - 2003
AIMS: To use echocardiography to determine early and late haemodynamic effects of atrio-biventricular (A-BiV) pacing on left ventricular (LV) function and their interrelations with exercise tolerance. METHODS: Thirty-four patients with ejection fraction <35% (18 idiopathic dilated cardiomyopathy (DCM) and 16 ischaemic cardiomyopathy, in sinus rhythm and with intra-ventricular conduction delay ...
Varma Chetan - - 2003
OBJECTIVES: We sought to assess the efficacy of biventricular pacing with respect to both peak and submaximal measures of exercise in patients with New York Heart Association class III heart failure (HF) and intraventricular conduction delay in a randomized, blinded study. BACKGROUND: Submaximal and maximal changes in exercise capacity need ...
Takenaka Kotoe - - 2003
BACKGROUND: Experimental studies suggest that the interval between peak and end of T wave (Tpe) in transmural ECGs reflects transmural dispersion of repolarization (TDR), which is amplified by beta-adrenergic stimulation in the LQT1 model. In 82 patients with genetically identified long-QT syndrome (LQTS) and 33 control subjects, we examined T-wave ...
Rajappan Kim - - 2003
BACKGROUND: QT interval prolongation occurs at rest and during exercise in pathological left ventricular hypertrophy. However, athletes with physiological hypertrophy have normal QT at rest. The aim of this study was to compare the effect of exercise on QT in athletes with echocardiographic left ventricular hypertrophy and normal controls, and ...
Yigit Zerrin - - 2003
The aim of this study was to investigate improvement in the cardiovascular response to isometric and isotonic exercises after reverting rhythm to sinus in patients with atrial fibrillation. Twenty seven cases with nonvalvular paroxysmal atrial fibrillation were included in the study. Sinus rhythm could not be restored in two cases ...
Cook Linnea - - 2003
This study examined the effects of adaptive rate pacing controlled by closed-loop right ventricular impedance sensing on exercise hemodynamics. Twelve patients in whom Biotronik INOS2+ pacemakers had been implanted 4-6 weeks earlier participated in the study. All patients completed two graded, symptom-limited exercise tests. The pacemaker was programmed to DDDR ...
Page Eric - - 2003
The authors previously have shown in healthy subjects that age related loss of muscular strength did not alter the chronotropic response during treadmill exercise, whether with sudden onset of effort, as in the chronotropic assessment exercise protocol (CAEP) or more gradual effort as in the Harbor exercise protocol. This study ...
Wang Lexin - - 2003
Congenital long QT syndrome (LQTS) is a group of ion channel disorders of ventricular myocytes caused by mutations of genes that encode these ion channels. The main clinical features of LQTS are syncope, cardiac arrest and QT prolongation on body surface electrocardiogram. The present study reports on the case of ...
Faes Luca - - 2002
A new method for quantifying the organization of single bipolar electrograms recorded in the human atria during atrial fibrillation (AF) is presented. The algorithm relies on the comparison between pairs of local activation waves (LAWs) to estimate their morphological similarity, and returns a regularity index (rho) which measures the extent ...
Duytschaever Mattias - - 2002
INTRODUCTION: Atrial pacing can reduce the number of recurrences of atrial fibrillation (AF). It is unclear the extent to which this effect is determined by the site(s) of pacing. METHODS AND RESULTS: In six electrically remodeled goats (24-hour AF), the window of inducibility of AF was determined by applying premature ...
Aliot Etienne - - 2002
The ablate and pace strategy may be considered a viable therapy in the palliative management of patients with medically refractory highly symptomatic atrial fibrillation (AF). The overall success rate is approaching 100%, the inhospital course is usually event free, and the procedure is a relatively safe therapeutic option. There is ...
Duru Firat - - 2002
Previous studies showed that transthoracic impedance minute ventilation (IMV), as measured by a pacemaker sensor, is closely correlated to actual minute ventilation (VE) determined by standard methods. The aim of this study was to analyze the changes in the calibration between IMV and VE at rest and during exercise over ...
Thompson K G - - 2003
The aim of this investigation was to determine the effect of even, negative and positive pacing on metabolic, kinematic and temporal variables during breaststroke swimming. Nine male swimmers [mean (SD): age 21 (3) years, height 178 (5) cm, body mass 77.2 (6.7) kg, 200 m-time 158.6 (13.6) s] completed a ...
van Loon G - - 2002
A five-year-old gelding suffered syncope at the end of a period of exercise. A 24-hour electrocardiogram recording revealed intermittent pauses in the sinus rhythm of up to 10 seconds, indicating sinus node disease; the pauses occurred repeatedly, particularly after exercise. A dual-chamber, rate-adaptive pacemaker was successfully implanted, which prevented excessive ...
MacAulay Kevin - - 2002
An Ibizan hound cross was referred with a 1-year history of syncope and exercise intolerance. An electrocardiogram showed bradycardia and no P waves; atrial standstill was diagnosed. A permanent artificial endocardial pacemaker was implanted. The lead dislodged and was reimplanted into the right ventricular apex. Capture was once again achieved.
Adebayo R A - - 2002
Most patients with sickle cell anaemia (SCA) show evidence of cardiac dysfunction. This study aimed at clinically and electrocardiographically assessing the exercise capacity of steady state SCA patients using self-paced walking exercise. Forty one (17 males and 24 females) steady state SCA patients between the ages of 15 and 37 ...
Fenelon Guilherme - - 2002
BACKGROUND: Human brain natriuretic peptide (hBNP) is a new therapeutic agent, nesiritide, indicated in patients with decompensated congestive heart failure, a group at significant risk of developing cardiac arrhythmias. Whether hBNP has cardiac electrophysiologic effects has not been reported. METHODS AND RESULTS: In 9 healthy, chronically instrumented, conscious dogs, hemodynamic ...
Miyazaki Hiroyasu - - 2002
The establishment of a new rate-correction method for the QT interval is presented for long-term telemetry ECG recording in free-moving beagle dogs. First, in order to define the QT-RR relation to derive the correction formula, the diurnal variations of the QT and RR intervals and the influencing factors were analyzed, ...
Richardson D A - - 2002
AIMS: To ascertain the reproducibility of the cardioinhibitory subtype of carotid sinus hypersensitivity (CICSH) in fallers. METHODS AND RESULTS: One hundred and seventy-five subjects with CICSH and unexplained or recurrent falls were randomized to pacemaker implantation or control. Sixty-four control subjects (61% female, mean age 71.8 years, median 2 falls ...
Sanders Prashanthan - - 2002
BACKGROUND: Atrial mechanical stunning develops on termination of chronic atrial arrhythmias and is implicated in the genesis of thromboembolic complications after cardioversion. The mechanisms responsible for atrial mechanical stunning are unknown. The effects of atrial rate, isoproterenol, and calcium on atrial mechanical function in patients with atrial stunning have not ...
Hirose Masamichi - - 2002
INTRODUCTION: Increased vagal tone significantly enhances susceptibility to atrial fibrillation (AF); however, the cellular mechanisms responsible for vagally mediated AF are not completely understood. METHODS AND RESULTS: In 12 isolated arterially perfused canine right atria, high-resolution optical mapping techniques were used to measure action potentials during control conditions, during intracardiac ...
Watanabe Ichiro - - 2002
The effect of rapid atrial pacing on the rate adaptation of the atrial action potential duration was studied in humans. The right atrial monophasic action potential (RAMAP) of 5 patients was recorded before and after 30 min of rapid atrial pacing. The pacing cycle length (CL) was 146 +/- 9 ...
Rashba Eric J - - 2002
INTRODUCTION: T wave alternans (TWA) is a heart rate-dependent marker of vulnerability to ventricular arrhythmias. Atrial pacing and exercise both are used as provocative stimuli to elicit TWA. However, the prognostic value of the two testing methods has not been compared. The aim of this prospective study was to compare ...
Manfredini Roberto - - 2002
The aim of this study was to examine 24h patterning in the symptoms indicative of third-degree atrio-ventricular (AV) heart block. We found a total of 227 cases (126 men and 101 women) of third-degree AV block that had been diagnosed by the Emergency Medical Department of the St. Anna Hospital ...
Zhong Ning - - 2002
AIM: To study the effects of 1-(2,6-dimethylphenoxy)-2-(3,4-dimethoxy-phenyl-ethylamino) propane hydro-chloride (DDPH) on the rapidly activating component (I(Kr)), and the slowly activating component (I(Ks)) of the delayed rectifier potassium current (I(K)) in guinea pig ventricular myocytes. METHODS: Whole-cell patch clamp recording techniques. RESULTS: DDPH (0.1-100 micromol/L) blocked the I(Kr) in a concentration-dependent ...
Davey Patrick - - 2002
Much inter- and intra-subject variability in the QT interval in health and disease is accounted for by differences in heart rate, leading to difficulties when determining the effects of disease and drugs on the QT interval. Traditionally, heart rate correction formulae have been used to overcome this problem in man. ...
Yamane Teiichi - - 2002
BACKGROUND:The pulmonary veins (PVs) have been shown to trigger paroxysmal atrial fibrillation. The relationship of anatomical dimensions versus arrhythmogenicity has not been assessed. METHODS: The diameters of four PVs were measured by selective PV angiography before ablation in 39 consecutive patients (23 male, mean age 46 years) with only one ...
Rinaldi C A - - 2002
The beneficial use of biventricular pacing is reported in a patient with hypertrophic cardiomyopathy and intraventricular conduction delay. This resulted in improvements in symptomatic status and exercise tolerance that may be related to cardiac resynchronisation. The improvement in symptoms by biventricular pacing in a patient with hypertrophic cardiomyopathy and intraventricular ...
Kannankeril Prince J - - 2002
Depressed parasympathetic tone is associated with an increased risk of sudden cardiac death. Exercise and the postexercise recovery period, which are associated with parasympathetic withdrawal, are high risk periods for sudden death. However, parasympathetic effects on cardiac electrophysiology during exercise and recovery have not been described. Electrophysiology studies were performed ...
Garrigue Stephane - - 2002
The rate responsiveness of a single chamber, accelerometer-based pacemaker with an autocalibration function (Opus G VVIR pacemaker, ELA Medical) was studied with a daily life protocol developed to automatically optimize the programming of accelerometer-based sensors. This new sensor was compared with two other body activity sensors that were manually optimized ...
Türker K S - - 2002
Synchronous discharges between a pair of concurrently active motoneurones are thought to arise from the spike-triggering effects of synaptic inputs shared by the pair. Although there are a number of quantitative indices that have been developed to estimate the strength of this common input, there is still some debate as ...
Hall G Martin - - 2002
We demonstrate that alternans in small pieces of in vitro paced bullfrog (Rana Catesbeiana) myocardium can be suppressed by making minute adjustments to the pacing period in response to real time measurements of the action potential duration. Control is possible over a large range of physiological conditions over many animals ...
Vogel Michael - - 2002
BACKGROUND: We have demonstrated that myocardial acceleration during isovolumic contraction (IVA) is a sensitive index of left ventricular contractile function. In this study, we assessed the utility of IVA to measure right ventricular (RV) contractile function. METHODS AND RESULTS: We examined 8 pigs by using tissue Doppler imaging of the ...
Severi Stefano - - 2002
The importance of plasma electrolytes and pH levels in determining heart rate is not yet well grounded. Hemodynamic and biochemical data were collected during 8 purely diffusive hemodialysis, which allowed changes in extracellular fluid to be achieved without eliciting notable changes in the autonomic control of heart rate. A significant ...
Carbone Vincenzo - - 2002
In a patient with right bundle branch block occurring on alternate beats during regular sinus rhythm, the conduction disturbance disappeared during hyperventilation induced increase in heart rate, and reappeared with slight slowing of the sinus rate due to carotid sinus massage. The following mechanisms are potentially involved in the electrogenesis ...
van Campen Linda C M C - - 2002
In patients with coronary artery disease (CAD), rate responsive pacing is considered to be contraindicated because an increase in heart rate may increase oxygen demand. Although previous studies have shown no subjective increase in ischemia during rate responsive pacing, data from objective assessment have not been documented. The goal of ...
Hexamer Martin P R - - 2002
Chronotropic incompetent patients are unable to adapt their heart rate adequately to the level of exertion. One treatment for this disease is a rate-responsive pacemaker that stimulates the heart at a rate proportional to an exertion-related variable derived from an implemented sensor (e.g., ventilation). The atrio-ventricular conduction time (AVCT), which ...
Silvetti M S - - 2002
Late survival after Mustard repair of transposition of the great arteries is generally good but is often characterized by progressive deterioration of ventricular function and by late postsurgical arrhythmias, thus imposing the need for permanent pacing. To evaluate how chronic pacing affects long-term exercise capacity, we compared two groups of ...
Altunkeser Bülent B - - 2002
It is known that the QT interval is longer in women than men. Estrogen is reported to account for the QT interval prolongation in several studies conducted with hormone replacement therapy (HRT) in postmenopausal women. Along with this, there are conflicting data as regards the effects of HRT on QT ...
Vieweg W Victor R - - 2002
This article reviews cardiac electrophysiology, with a focus on the assessment of the electrocardiographically determined corrected QT (QTc) interval and its role as a marker for potentially life-threatening cardiac arrhythmias such as torsades de pointes. Presently, using the QTc interval as a surrogate for polymorphic ventricular tachycardia is handicapped, in ...
Such L - - 2002
We have studied the intrinsic modifications on myocardial automatism, conduction, and refractoriness produced by chronic exercise. Experiments were performed on isolated rabbit hearts. Trained animals were submitted to exercise on a treadmill. The parameters investigated were 1) R-R interval, noncorrected and corrected sinus node recovery time (SNRT) as automatism index; ...
Cheng C W - - 2001
To facilitate the use of multileaf collimator (MLC) in field shaping, we tested the hypothesis that the changes in the penumbra due to MLC replacing a Cerrobend block can be related to a change in the margin of the block. We also investigated if it is possible to estimate the ...
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