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Results 101 - 150 of 1154
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Silberbauer John - - 2009
PURPOSE: The study aim was to validate the closed loop stimulation (CLS) vs. accelerometer (ACC) rate-responsive sensors with electrodes placed in the right ventricular high septal (RVHS) or right ventricular apical (RVA) lead positions in patients following 'ablate and pace' therapy for persistent atrial fibrillation. METHODS: 'Ablate and pace' patients ...
Baron B - - 2011
Thepacing strategy may be defined as the process in which the total energy expenditure during exercise is regulated on a moment-to-moment basis in order to ensure that the exercise bout can be completed in a minimum time and without a catastrophic biological failure. Experienced athletes develop a stable template of ...
Mokrani Bilel - - 2009
BACKGROUND: It is unclear whether, in recipients of cardiac resynchronization therapy (CRT) systems, the optimal AV delay should be the same, shorter, or longer during exercise than at rest. OBJECTIVE: This study sought to examine the effects of atrioventricular (AV) delay optimization at rest and during exercise in 50 recipients ...
Tucker R - - 2009
During self-paced exercise, the exercise work rate is regulated by the brain based on the integration of numerous signals from various physiological systems. It has been proposed that the brain regulates the degree of muscle activation and thus exercise intensity specifically to prevent harmful physiological disturbances. It is presently proposed ...
Tucker R - - 2009
The regulation of the pacing strategy remains poorly understood, because much of classic physiology has focused on the factors that ultimately limit, rather than regulate, exercise performance. When exercise is self-paced and work rate is free to vary in response to external and internal physiological cues, then a complex system ...
Passman Rod - - 2009
BACKGROUND: Atrial rate-adaptive pacing may improve cardiopulmonary reserve in patients with left ventricular dysfunction. METHODS: A randomized, blinded, single-crossover design enrolled dual-chamber implantable defibrillator recipients without pacing indications and an ejection fraction < or =40% to undergo cardiopulmonary exercise treadmill stress testing in both atrial rate-adaptive pacing (AAIR) and ventricular ...
Naffe Aster - - 2009
After pacemaker/implantable cardioverter-defibrillator (pacemaker/ICD) implantation, patients are often required to immobilize the affected arm with a sling to minimize the risk of lead displacement. We examined whether performing a resistive range-of-motion exercise protocol after pacemaker/ICD surgery would result in lead displacement and, therefore, whether sling immobilization and activity restrictions are ...
Wittmeier Steffen - - 2008
Inspiratory and expiratory rhythms in mammals are thought to be generated by pacemaker-like neurons in 2 discrete brainstem regions: pre-Bötzinger complex (preBötC) and parafacial respiratory group (pFRG). How these putative pacemakers or pacemaker networks may interact to set the overall respiratory rhythm in synchrony remains unclear. Here, we show that ...
Zhang Youhua - - 2009
BACKGROUND: Strong vagus nerve stimulation (VNS) is routinely used to induce and maintain atrial fibrillation (AF) in acute animal studies. Taken as a surrogate of increased vagal tone, such observations suggest an arrhythmogenic role of VNS in AF. In contrast, VNS has been demonstrated to have profound therapeutic effects in ...
Roux Jean-François - - 2009
BACKGROUND: Targeting of complex fractionated electrograms (CFEs) has been used as an adjunctive strategy to pulmonary vein isolation (PVI) in patients with persistent atrial fibrillation (AF). However, it is unclear whether CFEs should be targeted before or after PVI. OBJECTIVES: The purpose of this study was to examine the effect ...
Liu Hongyan - - 2008
Atrial fibrillation (AF) may cause thrombus formation in the left atrial appendage (LAA). Thrombus formation is associated with LAA endocardial dysfunction. Because asymmetrical dimethylarginine (ADMA) can cause endothelial dysfunction by decreasing nitric oxide (NO) formation, we investigated plasma ADMA and nitrite/nitrate (NO(X)) levels and myocardial dimethylarginine dimethylaminohydrolase-2 (DDAH-2), protein arginine ...
Laszlo R - - 2008
In rabbit, after short-time rapid atrial pacing (RAP), atrial ion currents are reduced similarly as in human chronic atrial fibrillation (AF). Using the rabbit model, time-course of transient outward potassium current (I(to)) remodeling due to RAP was studied. RAP (600 bpm) was applied via an atrial lead for 0 (control), ...
Berg Kris E - - 2008
The purpose of this study was to describe the pacing strategy of experienced cyclists in a 5-minute maximal exercise bout and to describe selected physiological responses associated with this effort. Six experienced and well-trained competitive cyclists (five males, one female) with a mean (+/-SD) age, height, and mass of 27.0 ...
Hina Kazuyoshi - - 2008
Cardiac resynchronization therapy (CRT) is theoretically expected to affect repolarization as well as depolarization. We studied the effects of CRT on corrected QT (QTc) dispersion in association with symptomatic improvement. QTc dispersion was analyzed in 26 consecutive patients (67 +/- 6 years old, 18 men and 8 women) who underwent ...
Valzania Cinzia - - 2008
Optimal exercise programming of cardiac resynchronization therapy (CRT) devices is unknown. We aimed to: (i) investigate variations in optimal atrioventricular (AV) and interventricular (VV) delays from rest to exercise, assessed by both echocardiography and an automated intracardiac electrogram (IEGM) method; (ii) evaluate the acute haemodynamic impact of CRT optimization performed ...
Moe Gordon W - - 2008
BACKGROUND: Atrial structural remodeling occurs in evolving heart failure (HF) and is an important substrate for the development of atrial fibrillation (AF). The matrix metalloproteinases (MMPs) play a role in extracellular remodeling, and recent studies have demonstrated increased atrial MMP activity in HF. Whether increased MMP activity directly contributes to ...
Pilat Eugeniusz - - 2008
AIMS: The aim of this study was to evaluate whether the use of a double sensor gives additional benefits for patients in improving physical efficiency as well as quality of life (QoL) as compared to the accelerometer sensor alone. METHODS AND RESULTS: The presented research is a prospective, randomized, single-blind ...
Schuchert Andreas - - 2008
BACKGROUND: The aim of the study was to compare the effects of different pacing strategies to prevent paroxysmal atrial fibrillation (AF): triggered atrial overdrive pacing versus the combination of triggered and continuous overdrive pacing. METHODS: Patients with an indication for dual-chamber pacing (Selection 9000, Prevent AF; Vitatron B.V., Arnhem, the ...
Zhou Tao - - 2008
BACKGROUND: Transcatheter closure is an effective approach for perimembranous ventricular septal defects (PMVSD). However, atrioventricular blocks (AVB) emerged possibly due to the close proximity of the PMVSD to the conduction system, but concern for the complication was not adequately emphasized. In this study, we report the incidence of AVBs, in ...
Liuba Ioan - - 2008
AIMS: Fractionated electrograms are often noted during mapping of focal atrial tachycardia (FAT). This finding suggests poor cell-to-cell coupling, which is thought to be an important prerequisite in the process of ectopic impulse initiation and propagation. The purpose of the present study was to assess the electrogram fractionation in the ...
Kannankeril Prince J PJ Oates Institute for Experimental Therapeutics, Clinical Research Center, Department of Biomedical Informatics, Vanderbilt University Medical Center, Nashville, Tennessee 37232-9119, USA. - - 2008
QT interval for a given heart rate differs between exercise and recovery (QT hysteresis) due to slow QT adaptation to changes in heart rate. We hypothesized that QT hysteresis is evident within stages of exercise and investigated which component of the QT contributes to hysteresis. Nineteen healthy volunteers performed a ...
Jost Norbert - - 2009
BACKGROUND: The aim of the present work was to study the profile of the rapid delayed rectifier potassium current (I (Kr)) and the inward rectifier potassium current (I (K1)) during ventricular repolarization as a function of action potential duration and rate of repolarization. METHODS: Whole cell configuration of the patch ...
Dalla Pozza Robert - - 2009
BACKGROUND: Turner syndrome (TS) is the most common sex chromosome abnormality in females. Recently, a prolongation of the rate-corrected QT (QTc) interval in the electrocardiogram (ECG) of TS patients has been reported. A prolonged QTc interval has been correlated to an increased risk for sudden cardiac death, and medical treatment ...
Arenal Angel - - 2008
BACKGROUND: Left atrium circumferential ablation (LACA) is a simple, effective treatment for atrial fibrillation (AF), but many pulmonary veins (PV) are not disconnected because of conduction gaps (CG) in the ablation line. OBJECTIVE: This study defined the electrogram characteristics at the CGs and at the PV- left atrium (LA) connection ...
Seki Yusuke - - 2008
To establish the electrophysiological mappings of nonhuman primates by using magnetocardiogram (MCG) data and obtain the normal values of MCG parameters, we used 64-channel superconducting quantum interference devices to measure 8x8 MCG data for 95 cynomolgus monkeys (Macaca fascicularis, 51 female and 44 male). The PQ interval, QRS duration, QT ...
Inger Ariansen
Background: The impact of atrial fibrillation (AF) on quality of life (QoL) differs with the AF population studied and is influenced by comorbidity. In hospital-based studies younger and highly symptomatic patients may be overrepresented. We performed an observational cross sectional study in two municipalities, comparing 75 year-old patients with and ...
Jeyaraj Darwin - - 2008
BACKGROUND: Patients with genetic evidence of long QT syndromes type 1 and 2 (LQT1, associated with impaired outward potassium current I(Ks); and LQT2, associated with impaired outward potassium current I(Kr)) may have normal baseline QT intervals (phenotype/genotype discordance) and elude clinical detection. Beta-adrenergic stimulation may unmask occult LQT1, but no ...
Anglesea Melissa M - - 2008
This study assessed the effects of a vibrating pager for increasing the duration of meal consumption in 3 teenagers with autism who were observed to eat too quickly. Participants were taught to take a bite only when the pager vibrated at predetermined intervals. A reversal design indicated that the vibrating ...
Koskela J - - 2008
OBJECTIVE: Cardiac repolarization is regulated, in part, by the KCNH2 gene, which encodes a rapidly activating component of the delayed rectifier potassium channel. The gene expresses a functional single nucleotide polymorphism, K897T, which changes the biophysical properties of the channel. The objective of this study was to evaluate whether this ...
Santomauro Maurizio - - 2008
BACKGROUND: Effective automatic mode switching (AMS) algorithms capable of detecting a range of supraventricular tachyarrhythmias is important given evidence of atrial fibrillation (AF), atrial flutter (AFL), and atrial tachycardia (AT) post-implantation of pacemakers. OBJECTIVES: The aim of the study was to assess the efficacy, defined as ability to detect a ...
Bailey Stephen P SP Department of Physical Therapy Education, Elon University , NC, - - 2008
Previous studies have shown changes in brain activity as a result of exercise; however, few studies have examined changes during exercise. The purpose of this study was to examine brain activity during a graded exercise test. Twenty male participants performed a graded exercise test on a recumbent cycle ergometer. Exercise ...
Whinnett Zachary I - - 2008
BACKGROUND: Atrioventricular (AV) optimization of cardiac resynchronization therapy (CRT) is typically calculated at rest. However, patients often become symptomatic during exercise. OBJECTIVE: In this study, we use acute noninvasive hemodynamics to optimize the AV delay of CRT during exercise and investigate whether this exercise optimum can be predicted from a ...
Melzer Christoph - - 2008
AIMS: Recommendations for programming the rate-adaptive AV delay in CRT. METHODS AND RESULTS: In cases of continual biventricular pacing, the optimal AV delay in CRT (AVD(opt)) is the net effect of the pacemaker-related interatrial conduction time (IACT), duration of the left-atrial electromechanical action (LA-EAC(long)), and the duration of the left-ventricular ...
Christenson Stuart D - - 2008
INTRODUCTION: Cardiac resynchronization therapy (CRT) can improve left ventricular (LV) hemodynamics and function. Recent data suggest the energy cost of such improvement is favorable. The effects of sequential CRT on myocardial oxidative metabolism (MVO(2)) and efficiency have not been previously assessed. METHODS AND RESULTS: Eight patients with NYHA class III ...
Sung Shih-Hsien - - 2008
BACKGROUND: The atrial substrate is the determinant of occurrence and maintenance of atrial fibrillation (AF), which can induce remodeling of atrial function and structure. This study investigated the relationship between the left atrial (LA) substrate properties and LA mechanical function. METHODS: Forty-four consecutive patients (50.3 +/- 10.7 years old, 33 ...
Nikoo Mohammad Hossein - - 2008
BACKGROUND: Emergence of junctional rhythm (JR) during radiofrequency (RF) current delivery directed at the periatrioventricular nodal region has been shown to be a marker of success in atrioventricular nodal reentrant tachycardia (AVNRT). Whereas the characteristics of JR during RF ablation of slow pathway have already been studied, the electrophysiologic features ...
Dunbar Christopher C - - 2007
A 28-yr-old female presented for preoperative evaluation. The resting ECG revealed sinus arrhythmia with complete heart block with a junctional escape rhythm and a ventricular rate of 43 bpm. The patient was in no apparent distress, and resting blood pressure was 80/50 mm Hg. Physical examination was largely unremarkable, with ...
Celestino Daniela - - 2007
Amiodarone is a potent antiarrhythmic drug commonly used in the treatment of supraventricular and ventricular arrhythmias. Dronedarone is a recently developed iodine-free compound (Sanofi Recherche), structurally related to amiodarone. Amiodarone and dronedarone have shown similar long-term effects on sinoatrial node automaticity in vivo and in vitro in the rabbit heart. ...
Drago Fabrizio - - 2007
BACKGROUND: A routine sports evaluation identified constant alternation between a junctional and idioventricular rhythm in a 9-year-old child. During exercise testing, electrography demonstrated that the child was in junctional rhythm without any apparent P waves, and had a reduced increase in heart rate. Endocardial atrial pacing captured the atrium and ...
Tadros Rafik R Département de physiologie, Faculté de médecine, Université de Montréal, Montréal, - - 2007
Rate-dependent AV nodal function is often assessed with premature protocols. Conduction curves generated from nodal responses differ with the selected recovery index (atrial-atrial, AA, or His-atrial interval, HA). We propose that these differences arise from changes in pretest conduction time that affect nodal recovery time assessment. We varied the basic ...
Brisinda Donatella - - 2007
Guinea pigs (GPs) are used for preclinical evaluation of electrophysiologic effects of new drugs, because their myocytes have human-like action potentials and ventricular repolarization's (VR) ion currents. This study was aimed to assess the reliability of magnetocardiographic (MCG) mapping for longitudinal studies of GP cardiac electrical activity. Eighteen anesthetized GPs ...
Zlatanovic Nenad - - 2007
OBJECTIVE: Adjusting pacemaker pulse amplitude influences the longevity of the pacemaker. Our aim was to establish the initial longevity gain. METHODS: Forty randomly selected patients with implanted pacemakers were analyzed. Mean age was 65.58+/-13.7 years. All pacemakers were working on factory settings of pulse amplitude 3.5 V and pulse width ...
Husser Oliver - - 2007
AIMS: Experimental studies suggest that the autonomic nervous system modulates atrial refractoriness and conduction velocity in atrial fibrillation (AF). These modulatory effects are, however, difficult to assess in the clinical setting. This study sought to non-invasively characterize in patients with persistent AF, the influence of autonomic modulation induced by exercise ...
Zaniboni Massimiliano - - 2007
Adaptation of action potential duration (APD) to pacing cycle length (CL) has been previously characterized in isolated cardiomyocytes for sudden changes in constant CL and for pre-/postmature stimuli following constant pacing trains. However, random fluctuations characterize both physiological sinus rhythm (up to 10% of mean CL) and intrinsic beat-to-beat APD ...
Lamas Gervasio A - - 2007
BACKGROUND: Ninety-nine percent of pacemakers implanted in the United States include an option for rate modulation. OBJECTIVE: The purpose of this study was to determine whether dual-chamber rate-modulated pacing, when compared with dual-chamber pacing alone, improved quality of life. METHODS: This was a single-blind randomized controlled trial comparing dual-chamber with ...
Daubert G Patrick - - 2007
We are presenting a case illustrating the complex metabolic and rhythm disturbances associated with acute clenbuterol intoxication. Clenbuterol is a long-acting beta2-adrenergic agonist primarily used in veterinary medicine in the United States. It has become a common drug of abuse by body builders because of its reported anabolic and lipolytic ...
Hekkala Anna-Mari - - 2007
INTRODUCTION: Many drugs are known to block cardiac potassium channels, thus prolonging QT interval and predisposing to malignant arrhythmias. Patients with congenital long QT syndrome are particularly vulnerable, but usually electrophysiological effects of drugs have not been assessed in these patients at risk. METHODS: Fifteen asymptomatic patients with type 1 ...
Dora S K - - 2007
Adenosine, used to terminate paroxysmal supraventricular tachycardia (SVT), is often useful in understanding the mechanism of tachycardia. This case report describes induction of SVT with adenosine in a 36-year-old man presenting with recurrent palpitations. After a short run of conduction via both slow and fast pathways, SVT was induced following ...
Soejima Yohkoh - - 2007
We conducted this study to verify the efficacy of atrial unipolar potentialfor for ablation of atrial tachycardia. The morphology of atrial unipolar potential at the successful and the best unsuccessful ablation sites was analyzed in 35 patients with atrial tachycardia (sino-atrial reentrant tachycardia (SART) 15, adenosine-sensitive atrial reentrant tachycardia near ...
Orio Francesco - - 2007
OBJECTIVE: The aim of the present study was to investigate the potential alterations in electrocardiographic (ECG) pattern in patients with polycystic ovary syndrome (PCOS). PATIENTS: Fifty PCOS patients and 50 age- and body mass index-matched healthy women were studied. METHODS: We assessed hormonal and metabolic pattern, and performed ECG analysis ...
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