Search Results
Results 151 - 200 of 1164
1 2 3 4 5 6 7 8 9 10 >
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 ...
Atwood J Edwin - - 2007
BACKGROUND: Therapy for chronic atrial fibrillation (AF) focuses on rate versus rhythm control, but little is known about the effects of common therapeutic interventions on exercise tolerance in AF. METHODS: Six hundred fifty-five patients with chronic AF underwent maximal exercise testing at baseline and 8 weeks, 6 months, and 1 ...
Brignole M - - 2007
BACKGROUND: Little is known of the variations of the heart rate during spontaneous cardioinhibitory neurally-mediated syncope. Their knowledge has both academic and practical implications for the optimization of rate drop response (RDR) pacing mode. METHODS AND RESULTS: We describe variations of the rhythm occurring during 48 syncopal episodes documented by ...
Melzer Christoph - - 2007
AIM: To optimize recommendations for programming of the rate-adaptive atrioventricular (AV) delay. METHODS AND RESULTS: Optimal AV delay (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 duration of left-ventricular latency (S(V)-EAC(short)). It can be calculated by AVD(opt) = ...
Roy Nelson - - 2007
OBJECTIVES: Differentiating adductor spasmodic dysphonia (ADSD) from muscle tension dysphonia (MTD) can be difficult. This investigation examined the precision of response to unilateral lidocaine block of the recurrent laryngeal nerve (RLN block) as a potential diagnostic test to discriminate ADSD from MTD. METHODS: Patients with ADSD (n = 23) and ...
Gao Dong-sheng - - 2007
BACKGROUND: Congenital long QT syndrome (LQTS) is an inherited ion channel disorder resulting in abnormal cardiac repolarization that can cause syncope and sudden death associated with a prolonged rate-corrected QT interval and polymorphic ventricular tachycardia. Several studies in adults showed that LQTS patients have altered QT adaptation to heart rate ...
Liang Wen-Chen - - 2007
Emery-Dreifuss muscular dystrophy (EDMD) is characterized by early-onset contractures, slowly progressive weakness, and muscle wasting in humeroperoneal muscles, and adult-onset cardiomyopathy with conduction block. We analyzed blood samples from an EDMD family, including a mother and two daughters, and found a novel mutation in codon 520 in exon 9 of ...
Ozdemir Ozcan - - 2007
Augmented sympathoadrenal activity during exercise may contribute to occurrence of various arrhythmias including atrial fibrillation (AF). The prolongation of intraatrial and interatrial conduction times and inhomogeneous propagation of sinus impulses are well-known characteristics of the atrium prone to fibrillate and are evaluated by maximum P-wave duration (P max), P-wave dispersion ...
Barbuti Andrea - - 2007
Activation of the pacemaker ("funny," I(f)) current during diastole is the main process underlying generation of the diastolic depolarization and spontaneous activity of cardiac pacemaker cells. I(f) modulation by autonomic transmitters is responsible for the chronotropic regulation of heart rate. Given its role in pacemaking, I(f) has been a major ...
Lum Jeremy J - - 2007
Spontaneous conduction during the supernormal period (SNP) of accessory pathways (AP) is rare and observed only during atrio-ventricular block (AVB). The effect of exercise and different escape rhythms on the SNP is unknown. We evaluated these factors on the SNP of a para-Hisian AP after a failed ablation complicated by ...
Extramiana Fabrice - - 2006
BACKGROUND: Following an abrupt change in heart rate (HR), QT adaptation is achieved within a delayed time frame. HYPOTHESIS: The exclusion of electrocardiograms (ECGs) showing rapid HR changes influences the level of a drug-induced QT prolongation. METHODS: Continuous 12-lead ECG-Holter monitoring was performed in 31 healthy subjects. Using the "bin" ...
Van de Veire Nico R - - 2007
We report the case of a 13-year-old girl with congenitally corrected transposition of the great arteries. Since the implantation of a conventional pacemaker for acquired complete atrioventricular block, the patient experienced increased heart failure symptoms. Using triplane tissue Doppler imaging, significant intraventricular dyssynchrony induced by unilateral pacing and associated with ...
Hu Xiao Sheng - - 2006
AIMS: The purpose of this study was to determine the relationship between pulmonary vein (PV) electrical activation during atrial fibrillation (AF) and after cardioversion into sinus rhythm. METHODS AND RESULTS: Electrograms were recorded using a circular mapping catheter during AF and after cardioversion in 53 PVs from 41 patients. Two ...
Ohmuro Junko - - 2006
Flagellar beating of hyperactivated golden hamster spermatozoa was analyzed in detail using digital image analysis and was compared to that of nonhyperactivated (activated) spermatozoa in order to understand the change in flagellar beating during hyperactivation and the active microtubule sliding that brought about the change in flagellar beating. Hyperactivated flagellar ...
Schmitt Michael W - - 2007
Electrocardiogram (ECG) QT interval prolongation produced by drugs in certain animal models is currently believed to be predictive of cardiac proarrhythmic effects in humans. For this reason, nonclinical assessment of the effects of novel drugs on cardiac repolarization is a regulatory prerequisite for progressing such agents to clinical evaluation. The ...
Hekkala Anna-Mari - - 2006
BACKGROUND: Accurate measurement of the QT interval is important for diagnosing long QT syndrome (LQTS), and in research on determinants of ventricular repolarization time. We tested automatic analysis of QT intervals from multiple ECG leads on chest. METHODS: Eleven healthy volunteers and 10 genotyped LQTS patients were tested at rest ...
Lewis M J - - 2006
The aim of the present study was to quantify the variability of electrocardiographic QT and RR intervals during rest and dynamic physical exercise, and to interpret these variabilities in terms of relative autonomic modulation of the atrial and ventricular myocardium. We also sought to characterize the relationships between QT, heart ...
Newbold Paul - - 2007
We sought to investigate subject specific QT interval correction factors (SSCF) determined at rest and after exercise and to determine the validity of these factors after the administration of a probe drug known to increase heart rate without directly affecting cardiac repolarization. Thirty-two healthy volunteers underwent graded exercise, multiple recordings ...
Knollmann Björn C - - 2007
Transgenic mice have been increasingly utilized to investigate the molecular mechanisms of cardiac arrhythmias, yet the rate dependence of the murine action potential duration and the electrical restitution curve (ERC) remain undefined. In the present study, 21 isolated, Langendorff-perfused, and atrioventricular node-ablated mouse hearts were studied. Left ventricular and left ...
Sasaki Osamu - - 2006
A young woman presented with takotsubo cardiomyopathy after a syncopal attack caused by torsades de pointes. Two-dimensional echocardiography on admission showed left ventricular apical akinesis (ballooning) and basal hyperkinesis, compatible with takotsubo cardiomyopathy. This gradually normalized in 2 months. ECG on admission showed remarkable QT prolongation, U waves, and negative ...
Tucker Ross - - 2006
PURPOSE: To analyze pacing strategies employed during men's world-record performances for 800-m, 5000-m, and 10,000-m races. METHODS: In the 800-m event, lap times were analyzed for 26 world-record performances from 1912 to 1997. In the 5000-m and 10,000-m events, times for each kilometer were analyzed for 32 (1922 to 2004) ...
Baspinar Osman - - 2007
Twelve children with a VDD/DDD pacemaker during 100, 125, 150, 200 ms atrioventricular delays and VVIR pacing, cardiac index was measured at rest and evaluated by endurance time during exercise stress test. The optimal atrioventricular delay, which provides highest cardiac index, was 100 ms in three, 125 ms in two, ...
Perhonen Merja A - - 2006
AIMS: High-intensity physical exercise and competitive sports have been traditionally avoided in long QT syndrome. However, endurance training increases vagal activity and thus may improve cardiac electrical stability in healthy subjects. We hypothesized that controlled submaximal endurance training would not adversely affect ventricular repolarization in asymptomatic carriers of a KCNQ1 ...
Earley Mark J - - 2006
OBJECTIVES: The aim of this study was to validate noncontact mapping (NCM) in the left atrium (LA) during sinus rhythm and atrial fibrillation (AF). BACKGROUND: Understanding the mechanisms of AF is crucial to the development of novel and effective treatments. Noncontact mapping records global electrical activation simultaneously and therefore has ...
Iakobishvili Z - - 2006
AIM: The occurrence of accelerated junctional rhythm during radiofrequency energy delivery at the region of the slow pathway is a well-recognized marker of successful treatment of atrioventricular nodal re-entry tachycardia (AVNRT). Our aim was to evaluate if the quantity and duration of accelerated junctional rhythm during radiofrequency ablation of the ...
Wess Gerhard - - 2006
We reviewed the indications for age and breeds of dogs who received transvenous endocardial artificial pacemaker (AP) implantation (n = 105) and complications and survival thereafter at a single institution over a 6-year period. A third-degree atrioventricular (AV) block (59%) and sick sinus syndrome (SSS; 27%) were the most common ...
Schuettpelz Eric - - 2006
The rate of molecular evolution is not constant across the Tree of Life. Characterizing rate discrepancies and evaluating the relative roles of time and rate along branches through the past are both critical to a full understanding of evolutionary history. In this study, we explore the interactions of time and ...
Krummen David E - - 2006
Periodic electrocardiographic RR intervals are often used to separate atrial flutter (AFl) from atrial fibrillation (AF), but have not yet been validated. We hypothesized that irregularly irregular electrocardiographic RR intervals poorly identify AF from AFl, and that atrial wavefront regularity affects variability in atrioventricular conduction. We studied the electrocardiographic RR ...
Kazemi Babak - - 2006
High-degree atrioventricular (AV) block during AV nodal re-entrant tachycardia (AVNRT) is considered a rare phenomenon. A patient with slow-fast AVNRT and transient high-degree AV block is presented. Electrophysiological manoeuvres identified the site of block in the lower common pathway of the AV node. This arrhythmia was rendered non-inducible after slow ...
Kligfield Paul - - 2006
QT-interval measurements have clinical importance for the electrocardiographic recognition of congenital and acquired heart disease and as markers of arrhythmogenic risk during drug therapy, but software algorithms for the automated measurement of electrocardiographic durations differ among manufacturers and evolve within manufacturers. To compare automated QT-interval measurements, simultaneous paired electrocardiograms were ...
Otomo Kiyoshi - - 2006
Focal left atrial tachycardias (AT) originating from the mitral annulus-aorta (MA-Ao) junction are rare and their mechanisms are unclear. We report a 35-year-old male with successful ablation of an exercise-induced focal AT due to triggered activity originating from the MA-Ao junction. The AT occurred spontaneously during treadmill exercise testing and ...
Eberhardt Frank - - 2006
INTRODUCTION: Sophisticated monitoring of atrial activity is a prerequisite for modern pacemaker therapy. Ideally, near-fields and ventricular far-fields ought to be distinguished by beat-to-beat template analysis of the atrial signal. A prerequisite is that atrial signals are stable under different conditions. METHODS AND RESULTS: A Matlab routine was developed to ...
Williams Gregory C - - 2006
INTRODUCTION: The effect of standing on heart rate and QT is well known but its impact on QTc is less clear. METHODS: Serial supine and standing 12-lead ECGs (seven pairs each day) were recorded from 54 healthy volunteers each day of a three-day period. ECGs were captured digitally and over-read ...
van den Berg Maarten P - - 2006
BACKGROUND: In patients with long-QT syndrome type 3 (LQT3), symptoms occur particularly at rest or during sleep. As to the underlying mechanism, excessive prolongation of the QT interval at slow heart rates probably plays a role. OBJECTIVES: The purpose of the present study was to investigate QT interval prolongation unrelated ...
Nakamoto Tomoko - - 2006
We have recently reported that the atrioventricular (AV) nodal mechanism functions to cancel fluctuation in the atrial excitation interval during a stair-stepping exercise. However, it remained unknown at which level of heart rate (HR) this mechanism started to operate and whether fluctuation in the interval might influence AV conduction over ...
Schmidt Matthias - - 2006
OBJECTIVE: There is controversy whether the measurement of QT dispersion might provide information about the presence and extent of ischaemic myocardium. It was the aim to analyse the diagnostic value of QT dispersion for the detection of myocardial ischaemia in comparison to Tl-201-SPECT. PATIENTS AND METHODS: 100 patients were randomly ...
Lewis M J - - 2006
The post-exercise electrocardiographic QT interval is shortened relative to that at similar heart rates during exercise or pre-exercise rest. This lag in QT adaptation to the recovering heart rate is described as "hysteresis". No previous studies have quantified the influence of ECG electrode placement on hysteresis following physical exercise. Six ...
Grygier M - - 2006
BACKGROUND: There are no reliable non-invasive markers of restenosis after percutaneous transluminal coronary angioplasty (PTCA). The aim of our study was to measure changes in QT interval dispersion after PTCA and to determine whether restenosis subsequently affects QT interval dispersion. METHODS AND RESULTS: Fifty-six consecutive patients - 41 men and ...
St Clair Gibson Alan - - 2006
This article examines how pacing strategies during exercise are controlled by information processing between the brain and peripheral physiological systems. It is suggested that, although several different pacing strategies can be used by athletes for events of different distance or duration, the underlying principle of how these different overall pacing ...
Wu Runze - - 2006
INTRODUCTION: Investigation of relationship between diastolic-interval (DI)-dependent restitution of action potential duration (APD) and alternans of APD has produced conflicting results. We used a novel pacing protocol to determine the role of restitution in alternans by minimizing changes in DI preceding each activation. METHODS: Transmembrane potentials were recorded from right ...
Melzer C - - 2006
AIMS: We prospectively evaluated results from cardiopulmonary exercise testing for chronotropic incompetence (CI) in a cohort of 292 pacemaker patients. In addition, we evaluated comorbidity and antiarrhythmic patient data as indicators of CI. METHODS AND RESULTS: On the basis of exercise stress testing and application of the definition of CI ...
1 2 3 4 5 6 7 8 9 10 >