Search Results
Results 201 - 250 of 1133
< 1 2 3 4 5 6 7 8 9 10 >
Cook Linnea - - 2005
BACKGROUND: The evaluation of the heart rate (HR) response to exercise is important for the assessment of the rate response algorithm of sensor-controlled pacemakers. This study examined the effects of a right ventricular impedance sensor driven pacemaker on the cardiovascular responses to incremental exercise in pacemaker dependent patients. METHODS: Twelve ...
Kok Lai Chow - - 2005
Pacing chronaxie can increase over time. The impact of a short pulse duration on threshold (THR) variations, frequency of noncapture episodes, and overall patient safety has not been fully studied. AutoCapture (AC) pacemakers are capable of memorizing THR trends and loss of capture (LOC) episodes. The study included 20 recipients ...
Tang Liang - - 2005
Protein C (PC), protein S (PS), antithrombin III, and plasminogen are four important anticoagulants in blood plasma. Deficiency of any of these biomolecules may lead to thrombo-embolic complications including lung embolism, heart attack, and stroke. A multi-factor sensing system is beneficial for identifying the cause of abnormal blood clotting more ...
Wolpert Christian - - 2005
The principal aim of this study was to assess the efficacy of quinidine in suppressing IKr in vitro and in modulating the rate dependence of the QT interval in the "SQT1" form of the short QT syndrome. Graded-intensity bicycle exercise testing was performed off drug in three patients and during ...
Extramiana Fabrice - - 2004
BACKGROUND: The short-QT syndrome is a new clinical entity characterized by corrected QT intervals <300 ms and a high incidence of ventricular tachycardia (VT) and fibrillation (VF). Gain-of-function mutations in the gene for outward potassium currents have been shown to underlie the congenital syndrome. The present study examined the cellular ...
Hexamer M - - 2004
Patients suffering from chronotropic incompetence are generally treated with a rate-responsive pacemaker that stimulates the heart at a rate derived from a strain related sensor signal. The pacemaker concept described here uses a well-defined time interval in the electrogram as sensor parameter (AVCT: atrio-ventricular conduction time). AVCT is directly controlled ...
Sanders Rob - - 2004
Following AVN ablation, eight dogs were surgically instrumented for chronic (continuous) HIS-bundle pacing. For data collection, implanted pacemakers were transiently programmed to pace in stepwise ascending ramps at rates from 50 to 200 beats/min in 30-beat/min steps. Each rate was held for 60 seconds. At each rate, ECG signals were ...
Zhang Hao - - 2004
AIM: To study the effect of capsaicin on carotid sinus baroreceptor activity (CBA). METHODS: The functional curve of carotid baroreceptor (FCCB) was constructed and the functional parameters of carotid sinus baroreceptor were measured by recording sinus nerve afferent discharge in anesthetized rats with perfused isolated carotid sinus. RESULTS: Low-concentration of ...
Erol-Yilmaz Ayten - - 2004
There are limited data about the chronotropic capacity of the peak endocardial acceleration (PEA) sensor. This study directly compared the chronotropic function from the PEA and the activity (ACT) sensor. The study included 18 patients (age 73 +/- 7 years) with > or = 75% pacemaker-driven heart rate (HR) and ...
Gelzer Anna R M - - 2004
BQ-123, a selective endothelin-A receptor antagonist, has been demonstrated to suppress arrhythmias. However, the role of physiologic levels of endogenous endothelin-1 (ET-1) with respect to electrophysiologic properties of the heart is unknown. BQ-123 (0.45, 0.9, 1.8, 3.6, 7.2, and 14.4 microg/kg/min; n = 10) or saline (control, n = 5) ...
Chauhan Vijay S - - 2004
Sudden intense physical activity is a trigger for ventricular arrhythmias in long QT syndrome (LQTS), and beta-blockers (B) reduce the risk of ventricular arrhythmias in LQTS. We compared the effect of graded (gradual intensity) versus burst (sudden intensity) exercise on QT-rate adaptation and T wave complexity in LQTS + B ...
Choi Bum-Rak - - 2004
INTRODUCTION: The restitution hypothesis proposes that adaptation of cardiac action potential duration (APD) to rate changes is a predictor of ventricular fibrillation (VF). Conventional restitution kinetics plots the APD of a premature beat as a function of the previous diastolic interval (DI), and VF vulnerability is related to how rapidly ...
Hexamer M - - 2004
The cardio-circulatory system of chronotropic incompetent patients is unable to adapt heart rate adequately to the level of strain. A common therapy is the implantation of a pacemaker that stimulates the heart at a rate derived from a strain related sensor signal. The paper describes a new pacemaker concept that ...
Dixit Sanjay - - 2004
Atrial Fibrillation (AF) is often initiated by pulmonary vein (PV) depolarizations. However, sustained PV firing (PVF) is infrequently observed in this population and has not been characterized. In 15 patients undergoing AF ablation we report the response of sustained PVF to pacing and pharmacological maneuvers. Sustained PVF was defined as ...
Mletzko Ralph - - 2004
Inappropriate therapy remains an important limitation of implantable cardioverter defibrillators (ICD). PARAD+ was developed to increase the specificity conferred by the original PARAD detection algorithm in the detection of atrial fibrillation (AF). To compare the performances of the two different algorithms, we retrospectively analyzed all spontaneous and sustained episodes of ...
De Pauw M - - 2004
OBJECTIVE: Myocardial contractility is regulated by adrenergic stimulation, the strength-length relationship and the force-frequency relationship or Bowditch effect. The latter mechanism was clearly demonstrated in muscle strips, in the isolated heart as well as in in-vivo experiments. The aim of this study was to further investigate the role of the ...
Gaudio C - - 2004
A 82-years-old man, symptomatic for fatigue and lypothymia, was referred to our centre in order to evaluate the opportunity of a permanent pacemaker insertion. A 12-lead ECG was described as a Mobitz type II second-degree atrioventricular block with 2:1 conduction. This surface ECG revealed some sinus beats with normal AV ...
Urao Norifumi - - 2004
A patient with idiopathic long QT syndrome had repeated syncopal episodes. The QTc interval on the electrocardiogram at rest was 530 ms and was prolonged by exercise up to 740 ms with T wave alternation. Intravenous epinephrine (0.1 microg/kg weight per min), but not isoproterenol (0.7 microg/min), produced early after ...
Dilaveris Polychronis - - 2004
BACKGROUND: Ibutilide is used for the pharmacologic cardioversion of atrial fibrillation (AF) or flutter (AFl). Ibutilide-induced QT interval prolongation has been demonstrated previously. However, its effects on vectorcardiographic (VCG) descriptors of ventricular repolarization (VR) have not been studied so far. HYPOTHESIS: To evaluate the effects of ibutilide on electrocardiographic (ECG) ...
Saxena Ashok K - - 2004
Right stellate ganglion block (SGB) can increase QT interval, rate-corrected QT interval (QTc), QT dispersion (QTD), rate-corrected QTD (QTcD), and RR interval while left SGB can decrease these intervals in healthy volunteers. No such studies have been conducted in patients with chronic pain, hence this study was designed to investigate ...
Ono Takashi - - 2004
In order to elucidate the beat-to-beat changes of the systolic time intervals (STI) during exercise, we proposed new techniques relating to an adaptive filter and detection algorithms for B- and X-points in the impedance cardiograph (ICG). Six male subjects underwent a ramp bicycle exercise up to maximum intensity during which ...
Shan Zhaoliang - - 2004
INTRODUCTION: During atrial fibrillation (AF), there is fractionation of extracellular potentials due to head-to-tail interaction and slow conduction of fibrillation waves. We hypothesized that slowing of the rate of AF by infusion of a Class I drug would increase the degree of organization of AF. METHODS AND RESULTS: Seven goats ...
Matsumoto Miwa - - 2004
BACKGROUND: Reduced variability of the ventricular response interval (VRI) has been reported to predict adverse prognosis in patients with atrial fibrillation (AF). To examine whether it could be related also to the quality of the daily life of patients with AF, the relationships between VRI variability and exercise tolerance, one ...
Kasikcioglu E - - 2004
Screening for cardiac health should involve relevant parameters or indices that are easy and inexpensive to obtain. Various cardiac adaptation mechanisms develop during regular exercise that are affected by many factors, and these are reflected on a surface electrocardiogram. QT dispersion has been considered a surrogate for heterogeneity of repolarization, ...
Barutcu Irfan - - 2004
BACKGROUND: Isolated myocardial bridging (MB) often is considered to be an unimportant angiographic finding; however, its association with cardiovascular event has been shown. In this study we aimed to assess exercise-induced electrocardiographic (ECG) changes and susceptibility to arrhythmia in patients with MB. METHOD: 21 consecutive patients who had angiographically proven ...
Banville Isabelle - - 2004
INTRODUCTION: The dependence of action potential duration (APD) on the preceding diastolic interval (DI), i.e., restitution, has been purported to predict the development of alternans and reentrant arrhythmias. However, restitution depends on the history of activation (i.e., memory), and its relevance to arrhythmia induction and maintenance is unknown. METHODS AND ...
Nakashima Hideko - - 2004
OBJECTIVES: This study evaluated the in vivo electrophysiological effects of a highly selective slow delayed-rectifier K+-current blocker, HMR 1556, to gain insights into the consequences of selectively inhibiting the slow delayed-rectifier current in vivo. METHODS: Atrial and ventricular effective refractory periods, sinus node recovery time, Wenckebach cycle-length, atrial fibrillation duration ...
Hua Fei - - 2004
Previous modeling studies have suggested that the rapid component of the delayed rectifier (I(Kr)) may contribute importantly to action potential dynamics during tachycardia. To test this idea experimentally, I(Kr) was measured as the E-4031-sensitive current in isolated canine endocardial myocytes at 37 degrees C using the perforated patch-clamp technique. Command ...
Schnitz Benjamin A - - 2004
While there is extensive mapping of the spread of electrical activity in the heart, there have been no measurements of electrical and localized mechanical, or contractile, activity. Yet the development of effective treatments for diseases like chronic heart failure and cardiac hypertrophy depend on the ability to quantify improvements in ...
Minami Takako - - 2004
Nifekalant, a class III antiarrhythmic drug, has been shown to suppress ventricular tachyarrhythmias, but its effects on AF are unclear. The aim of this study was to clarify the effects of nifekalant on the atrial vulnerability parameters in patients with paroxysmal AF. The study included 18 patients with paroxysmal AF ...
Thompson Kevin G - - 2004
Performances often vary between the heats and finals of breaststroke swimming competitions possibly because the swimmers try to conserve their energy, or for other tactical reasons. Additionally, coaches might advise either a 'positive' or 'even' pace race strategy during the final. The effect of such pacing changes on metabolism (blood ...
Wu Runze - - 2004
Restitution of action potential duration (APD) is thought to be critical in activation instability. Although restitution is used to predict APD during sequential changes in diastolic interval (DI), currently used protocols to determine restitution do not use sequential changes in DI. We explored restitution using a new pacing protocol to ...
Dell'Orto Simonetta - - 2004
Advances in pacemaker technology in the 1980s have generated a wide variety of complex multiprogrammable pacemakers and pacing modes. The aim of the present review is to address the different rate responsive pacing modalities presently available in respect to physiological situations and pathological conditions. Rate adaptive pacing has been shown ...
Ryu K - - 2004
A stable rhythm of very short cycle length (CL) in the left atrium (LA) can cause fibrillatory conduction, particularly in the right atrium (RA). Fast Fourier transform (FFT) analysis reliably identifies LA to RA conduction path(s) during atrial fibrillation (AF). We tested the hypotheses that FFT analysis of atrial electrograms ...
Ozin Bulent - - 2004
Tachycardia induced tachycardias are not common in clinical practice, and it is believed that most cases of double tachycardia are coincidental. The existence of two different tachycardias in the same patient almost always poses problems in the electrophysiology laboratory. However, in rare instances, the emergence of a second tachycardia can ...
Zhao Ding - - 2003
AIM: To compare the effects of moxonidine (Mox), clonidine (Clo), agmatine (Agm), and xylazine (Xyl) on action potentials (AP) of the rabbit sinoatrial node (SAN) pacemaker cells and investigate the contribution of alpha-adrenoceptors to the cardiac electrophysiologic responses induced by the agonists. METHODS: Intracellular microelectrode technique was used to record ...
Puglisi A - - 2003
AIMS: Atrial overdrive pacing algorithms increase Atrial Pacing Percentage (APP) to reduce Atrial Tachyarrhythmia (AT) recurrences in patients with Brady-Tachy Syndrome (BTS). This study aimed to compare AT burden and APP in BTS patients treated with conventional DDDR pacing, DDD+ overdrive or Closed-Loop Stimulation (CLS). METHODS AND RESULTS: One hundred ...
Moriguchi Masahiko - - 2003
Verapamil is known to suppress shortening of the atrial effective refractory period (AERP) during relatively short-term atrial pacing, although the effect of a long-term stimulation model is unclear. The effect of verapamil on electrical remodeling was evaluated in a canine rapid atrial stimulation model. The right atrial appendage (RAA) was ...
Colin Patrice - - 2004
Lowering heart rate reduces myocardial oxygen consumption (MVO2) and produces potent anti-ischemic effects. The development of selective heart rate-reducing agents represents an alternative approach to the use of beta-blockers. Therefore, our goal was to establish the dose-response curve of the effects of ivabradine (If channel inhibitor) on MVO2 and diastolic ...
Sanders Prashanthan - - 2003
BACKGROUND: Atrial mechanical "stunning" develops after cardioversion of atrial fibrillation (AF) and is implicated in the genesis of thromboembolic complications. However, the mechanisms responsible for this phenomenon are poorly understood. Whether atrial mechanical dysfunction caused by AF can be reversed by pacing at increased rates or by pharmacological agents is ...
Maurer D E - - 2003
AIMS: The aim of this study was to assess quality of life (QoL) and exercise capacity during permanent ventricular stimulation (PVS) compared with intrinsic atrioventricular conduction (IAVC) in patients with dual chamber pacemakers (PMs) and an intrinsic PQ interval >210 ms. Dual chamber PMs in patients with atrioventricular (AV) block ...
Miura Naoki - - 2003
Permanent pacemakers are commonly used in veterinary practice and can have a dramatic effect on the treatment of heart block. A Labrador Retriever dog suffering from exercise intolerance secondary to third degree atrioventricular block was treated with a new pacemaker system. A steroid-eluting screw-in type lead that has the advantage ...
Brouwer Jan - - 2003
BACKGROUND: Recently, we identified a novel mutation of SCN5A (1795insD) in a large family with LQTS3. The aim of this study was to assess whether the various proposed corrections of the QT interval to heart rate help to improve the identification of carriers of the mutant gene. METHODS: The study ...
Yiğit Zerrin - - 2003
AIM: Prolongation of P wave time and increase of its dispersion as an independent predictor of atrial fibrillation. In patients with paroxysmal atrial fibrillation (PAF) as in healthy people, exercise augments sympathetic activity and therefore can cause the development of atrial fibrillation. The aim of this study is to evaluate ...
Wozakowska-Kapłon Beata - - 2003
BACKGROUND: Loss of atrial systolic function as well as fast and irregular ventricular response result in the impairment of hemodynamic function in patients with atrial fibrillation (AF). AF is considered to be a less efficient cardiac rhythm than sinus rhythm (SR), and accounts for the symptoms of reduced exercise tolerance, ...
Hulot Jean-Sébastien - - 2003
AIMS: Women have a longer QT interval and a greater incidence of torsades de pointes than men. It has been suggested that oestrogens may influence the duration of cardiac repolarization. We thus investigated the influence of oestradiol (E2) on ventricular repolarization within the physiological concentration range of this hormone. METHODS ...
Shimizu Akihiko - - 2003
INTRODUCTION: The aim of this study was to investigate the usefulness of the autocorrelation function (reversed fast Fourier transform analysis) in determining the atrial fibrillation cycle length (AFCL) during human atrial fibrillation (AF). METHODS AND RESULTS: From 30 episodes of atrial electrograms recorded for 30 seconds from the high right ...
Andrássy Gábor - - 2003
This study assesses the effect of a first cigarette smoked in the morning on the QT interval duration in healthy habitual smokers after not smoking overnight. This study demonstrates that although after cigarette smoking the QT(Bc) values increase, the QT(Fc) and QT(Lc) values remained unchanged, and an increased sympathetic response ...
Rivero-Ayerza M - - 2003
A 73-year-old man had a fast atrioventricular (AV) nodal pathway accidentally ablated 4 years before, while attempting to ablate a septally located concealed accessory pathway (AP). After initiation of treatment with beta-blockers, because of systemic arterial hypertension, the patient presented to the emergency room complaining of a markedly diminished exercise ...
Ishii Yosuke - - 2003
BACKGROUND: Incisional atrial reentrant tachycardia is a life-threatening tachyarrhythmia after surgery for congenital heart disease. Slow conduction through an isthmus between anatomical barriers, such as a right atriotomy or the sites for cannulation, has been shown to be a prerequisite for perpetuation of the incisional atrial reentrant tachycardia. However, the ...
< 1 2 3 4 5 6 7 8 9 10 >