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Results 351 - 400 of 1154
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Sternick E B - - 2001
Concealed AP with Slow and Incremental Conduction. We report a peculiar form of permanent junctional reciprocating tachycardia that occurs only during daytime and physical activity. ECG obtained during tachycardia showed an unusual progressive shortening of the ventriculoatrial (VA) interval that was maximal at the first complex and shortest at the ...
Sato K - - 2001
PURPOSE: To clarify the clinical significance of QT dispersion and the longest QT intervals (L-QTc) in patients with subarachnoid hemorrhage (SAH). METHODS: ECGs, clinical features, and laboratory data were analyzed in 38 patients with SAH (R) and 30 with unruptured cerebral aneurysms (U). Standard 12-lead ECGs obtained on admission were ...
Newton J C - - 2001
INTRODUCTION: Recent studies showed that pacing atrial and ventricular fibrillation (VF) is possible. The studies presented here determined which parameters influence the efficacy of a pacing train to capture fibrillating ventricular myocardium. Electrode type, current strength, order of pacing trains, polarity, and VF morphology preceding the pacing trains were investigated. ...
Kochiadakis G E - - 2001
AIMS: To compare the effects of sotalol and metoprolol on heart rate, during isotonic (ITE) and isometric (IME) exercise and daily activities, in digitalized patients with chronic atrial fibrillation. METHODS AND RESULTS: The study had a randomized, single-blinded, crossover design. Twenty-three patients with chronic atrial fibrillation received placebo for 4 ...
Howes C J CJ Yale School of Medicine New Haven, CT, - - 2001
Atrial fibrillation is the most common arrhythmia affecting the elderly. Although the risk of cardioembolic stroke is well defined, the effects of chronic atrial fibrillation on exercise tolerance and quality of life have been less well quantified. We compared a group of 52 elderly patients with chronic atrial fibrillation to ...
Provenier F - - 2000
The Autocapture feature, implemented in the Microny and Regency pacemakers of St. Jude Medical, continuously controls the effectiveness of ventricular stimulation by detection of the evoked response. Proper sensing of this signal depends on the magnitude of the polarization, which should be minimal. Therefore, the conjunctive use of low polarization ...
Gögelein H - - 2000
Chromanol HMR 1556 [(3R,4S)-(+)-N-[3-hydroxy-2,2-dimethyl-6-(4,4,4-trifluorobutoxy)chroman-4-yl]-N-methylmethanesulfonamide], a novel inhibitor of the slow component of the delayed outward current in heart muscle cells (IKs), has been characterized in several in-vitro systems. mRNA encoding for the human protein minK was injected into Xenopus oocytes, leading to the expression of IKs channels. HMR 1556 inhibited ...
Israel C W - - 2000
Rate-adaptive pacing has been shown to improve exercise capacity in patients with chronotropic incompetence. However, all sensors used to adapt the pacing rate to meet metabolic demands show typical limitations. To overcome these, concepts using 2 sensors for rate adaptation have been developed, combining an unspecific but fast-reacting sensor with ...
Braith R W - - 2000
BACKGROUND: Chronotropic incompetence is one cause of diminished exercise capacity in heart transplant recipients. If reinnervation occurs, it often is late after transplantation and is not always accompanied by functional improvements in peak heart rate and appropriate tachycardia during exercise. To determine the efficacy of rate-responsive pacing on peak heart ...
Page E - - 2000
Cardiopulmonary exercise tests are frequently used to test rate responsive pacemakers. The chronotropic assessment exercise protocol (CAEP) has been specifically proposed for the evaluation of rate responsive pacing systems. A mathematical method, based on CAEP measurements, was developed with a view of normalizing the exercise induced metabolic response. CAEP was ...
Pladys P - - 2000
The objective was to test if changes in autonomic tone still influenced the RT-RR relationship when full RT adaptation is completed, when heart rate is controlled, and when beat-to-beat variability is abolished by atrial pacing. Eight dogs (8-11 kg) were chronically instrumented with atrial pacing electrodes. Digital ECG (1,000 Hz, ...
Yi G - - 2000
Premature sudden cardiac death (SD) is a critical event in the natural history of hypertrophic cardiomyopathy (HCM), and occurs during or just after physical exertion in approximately 60% of instances. Abnormalities in ventricular repolarization may not be present at rest in some patients but may become apparent under certain conditions. ...
Zabel M - - 2000
OBJECTIVES: The study was done to determine whether variables of QT dispersion from the 12-lead electrocardiogram (ECG) are dependent on heart rate. BACKGROUND: The dispersion of the QT interval is under evaluation as a risk marker in patients at risk for ventricular arrhythmias. Assuming that a similar rate correction is ...
Leung S K - - 2000
Peak endocardial acceleration (PEA) measured by an implantable acceleration sensor inside the tip of a pacing lead reflects ventricular filling and myocardial contractility. The contribution of the plateau phase of PEA as an indicator of optimal ventricular filling, hence of the appropriate atrioventricular interval (AVI) at rest and during exercise, ...
Meine M - - 2000
The evaluation of the heart rate response to exercise is important for the diagnosis of chronotropic incompetence and the assessment of a rate responsive algorithm of sensor-controlled pacemakers. The aim of the present study was to examine a classification of the chronotropic response at an individually moderate exercise level. Sixteen ...
White R L - - 2000
To examine the relationship between mitochondrial NADH (NADH(m)) and cardiac work output, NADH(m) and the amplitude and frequency of the contractile response of electrically paced rat heart cells were measured at 25 degrees C. With 5.4 mM glucose plus 2 mM beta-hydroxybutyrate, NADH(m) was reversibly decreased by 23%, and the ...
Peralta A O - - 2000
OBJECTIVES: We sought to study the rate related effects of sotalol on myocardial contractility and to test the hypothesis that the class III antiarrhythmic effect of sotalol has a reverse use-dependent positive inotropic effect in the intact heart. BACKGROUND: Antiarrhythmic drugs exert significant negative inotropic effects. Sotalol, a beta-adrenergic blocking ...
Ndrepepa G G Deutsches Herzzentrum München and 1. Medizinische Klinik, Klinikum rechts der Isar, Technische Universität München, Munich, - - 2000
Linear lesions (LL) represent an option for curing of atrial fibrillation (AF) with ablation techniques. In 11 sheep (w. 72+/-16 kg), LL were created with radiofrequency ablation in the lateral, posterior and septal walls of the right atrium (RA). AF was induced before and after LL with burst pacing. Mapping ...
Burri H - - 2000
To determine the characteristics of QT interval dispersion using orthogonal ECG leads with high paper speed (100 mm/s) and high voltage gain (10 cm/mV) as compared to conventional 12-lead ECG, we measured the QT dispersion in 57 patients at rest and directly after exercise using these two techniques. The measurements ...
Mansfield C S - - 2000
A six-year-old Staffordshire bull terrier had a four-week history of progressive lethargy, ascites and exercise intolerance. A mass 3 cm in diameter obliterating the right atrial lumen was detected by echocardiographic examination. There were lactescent pericardial and serosanguineous pleural effusions. Histological and immunochemical examinations showed that the mass was a ...
Ijiri H - - 2000
We used a cardiopulmonary test to assess the physiological benefit of single lead VDD pacing in ten patients (six men, four women; aged 32-84 years, mean 69 years) with atrioventricular block. Maximal symptom-limited treadmill exercise test using a ramp protocol was performed under VDD and VVIR or VVI pacing (VVI) ...
di Bernardo D - - 2000
QT interval dispersion may provide little information about repolarization dispersion. Some clinical measurements demonstrate an association between high QT interval dispersion and high morbidity and mortality, but what is being measured is not clear. This study was designed to help resolve this dilemma. We compared the association between different clinical ...
Sharifov O F - - 2000
INTRODUCTION: Prior studies in isolated canine atria demonstrated that acetylcholine-induced reentrant atrial fibrillation (AF) was triggered by multifocal activity in the area of normal impulse origin (sinus node-crista terminalis). The aim of this study was to investigate the activation sequence in AF induced by vagal stimulation (VS) in intact dog ...
Heaven D J - - 2000
An 8-year-old boy with Wolff-Parkinson-White syndrome died suddenly whilst exercising. He had been well with no immediate preceding symptoms of an arrhythmia, and was receiving no drugs. As an infant he had suffered recurrent episodes of atrioventricular reciprocating tachycardia (AVRT) and had documented pre-excited atrial fibrillation. At electrophysiological (EP) study, ...
Fan L - - 2000
ECGs free of movement artefacts were obtained without anesthesia in 16- to 18-day-old chick embryos close to hatching and used to study the effect of the environmental toxin 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD) on cardiac rhythm and conduction. The ECGs of normal late stage chick embryos exhibited short PR intervals, frequent nonisoelectric ...
Nakashima H - - 2000
The blockade of angiotensin II (Ang II) formation has protective effects on cardiovascular tissue; however, the role of Ang II in atrial electrical remodeling is unknown. The purpose of this study was to investigate the effects of candesartan and captopril on atrial electrical remodeling. In 24 dogs, the atrial effective ...
van der Velden H M - - 2000
OBJECTIVE: It has been postulated that high atrial rate induced changes at the level of the gap junctions ('gap junctional remodeling', i.e. changes in distribution, intercellular orientation and expression of gap junction proteins), could be part of the vicious circle of electrophysiologic and structural changes leading to sustained atrial fibrillation ...
Maguire C T - - 2000
INTRODUCTION: Dual AV nodal physiology is characterized by discontinuous conduction from the atrium to His bundle during programmed atrial extrastimulus testing (A2V2 conduction curves), AV nodal echo beats, and induction of AV nodal reentry tachycardia (AVNRT). The purpose of this study was to characterize in vivo murine maturational AV nodal ...
Lee J W - - 2000
Vaginocervical stimulation (VCS) received during mating is known to induce analgesia and to suppress FOS-immunoreactivity (FOS-IR) in lumbar spinal cord. However, it is not known whether this suppression of FOS-IR reflects inhibition of afferent nociceptive input. The present studies examined whether two immediate-early gene (IEG) products, FOS and Egr-1, covary ...
Toeda T - - 2000
A 54-year-old man with normal atrioventricular (AV) conduction at rest gave a 4-year history of presyncope during exercise. Treadmill testing showed exercise induced AV block. Electrophysiological study demonstrated rate dependent infranodal AV block and abnormal refractory period of the His-Purkinje system. The gap phenomenon in AV conduction occurred during the ...
Shoji S - - 2000
INTRODUCTION: In the development of atrial flutter due to reentry, the crista terminalis is supposed to pose a conduction barrier, but the role of its longitudinal conduction in determining the propagation pattern of the reentrant impulse is not known. In rabbit right atrial preparations, we induced reentrant atrial tachycardias and ...
Lowe M D - - 2000
A 29-year-old man developed recurrent syncope following exertion. Cardiac investigations revealed no evidence of structural heart disease, but during exercise testing, in the recovery phase, he sustained a bradycardia and then asystole for a prolonged period. Before cardiac massage could be instituted a tonic-clonic fit occurred, and this initiated a ...
Strobel J S - - 2000
The chronotropic response is the most important means by which cardiac output is increased and oxygen delivery is maintained in response to increased oxygen consumption during exercise or stress. When the chronotropic response is suboptimal or absent, exercise intolerance results. This condition, called chronotropic incompetence can be treated effectively with ...
Shafik A - - 2000
BACKGROUND AND PURPOSE: Our previous studies have demonstrated that rectal electric waves start at the rectosigmoid junction (RSJ) and spread caudad along the rectum. A rectosigmoid pacemaker was postulated to exist at the RSJ. We also demonstrated that electric waves in rectal inertia are so scarce that a "silent" electrorectogram ...
Rickli H - - 2000
It has been shown that dual chamber pacing with preservation of AV synchrony (DDD) is superior to fixed rate ventricular (VVI) or rate responsive ventricular (VVIR) pacing modes, as evaluated by ventilatory response to exercise. Previous studies have focused on the benefits of maintained AV synchrony at maximal exercise. However, ...
Iliev I I - - 2000
The purpose of the study was to compare the effects of DDD pacing with optimal AV delay and AAI pacing on the systolic and diastolic performance at rest in patients with prolonged intrinsic AV conduction (first-degree AV block). We studied 17 patients (8 men, aged 69 +/- 9 years) with ...
Brunner-La Rocca H P - - 2000
Automatic mode switching from DDD(R) to DDI(R) or VVI(R) pacing modes has improved dual chamber pacing in patients at high risk for supraventricular tachyarrhythmias. However, little is known about the effect of ventricular pacing rate adaptation after mode switching. We conducted a single-blinded, crossover study in 15 patients (58 +/- ...
Abo M - - 2000
The aims of this study were to investigate the effect of duodenal distension on intestinal myoelectrical activity and to investigate whether intestinal pacing was able to reverse the effects of distension. Six female hound dogs with four pairs of electrodes on the proximal jejunum were involved in this study. The ...
Ishikawa T - - 2000
Although sinus node recovery time (SNRT) assessment by the overdrive suppression test (ODST) is important in detecting sick sinus syndrome (SSS), its sensitivity is still inadequate. We have evaluated the effect of intravenous injection (i.v.) of disopyramide phosphate (DP) in ODST. The subjects were 30 SSS patients (64.9 +/- 10.0 ...
Glotzer T V - - 1999
We present the case of a patient with a dual chamber implantable cardioverter defibrillator (ICD) who experienced inappropriate ICD discharges during exercise. Interrogation of the ICD revealed intermittent atrial undersensing during exercise that was responsible for the erroneous classification by the ICD of sinus tachycardia as ventricular tachycardia. Monitoring of ...
Alexander C - - 1999
Atrial fibrillation (AF) is a common cardiac arrhythmia that becomes more common as patients get older. We review the common factors associated with AF and hemodynamic abnormalities. In addition, we discuss practical management issues concerning treatment of patients with rapid, hemodynamically significant AF, as well as patients with hemodynamically stable ...
Lehmann G - - 1999
This report concerns a 74-year-old patient who had undergone aortic valve replacement 11 years earlier. On admission, the patient complained of shortness of breath when climbing two flights of stairs; there was no history of dizziness, fainting or sensations of arrhythmias. An ECG at rest showed first-degree atrioventricular (A-V) block ...
Meine M - - 1999
The dromotropic pacemaker concept needs a rate responsive algorithm in which the pacing rate is controlled by the atrioventricular conduction time (AVCT). To develop basic concepts for such a rate responsive algorithm, the influence of the pacing rate on the AVCT was investigated. Seven patients (62 +/- 7.8 years) with ...
Guyomar Y - - 1999
If atrial sensing ability of a single-lead VDD pacemaker is well accepted at rest, the detection quality by atrial floating electrodes remains less recognized during exercise. The aim of this study was to verify, during treadmill test and a continous telemetry, the atrial tracking performance using four different leads technologies. ...
Yetkin E - - 1999
There is still controversy about the reliability and prognostic value of QT interval dispersion because of interobserver and intraobserver variability. The authors aimed to study the effect of respiratory phases on QT dispersion. Sixty healthy volunteers (38 men, 22 women, mean age 25+/-3 years) from the medical staff comprised the ...
Blaauw Y - - 1999
Atrial fibrillation (AF) shortens the atrial effective refractory period (AERP). To investigate the role of the autonomic nervous system during this so-called electrical remodeling of the atria (ERA) and during recovery from ERA we analyzed heart rate variability (HRV). In 12 goats atrioventricular (300:150 beats/min) pacing was performed for 24 ...
Schauerte P N - - 1999
INTRODUCTION: Epicardial electrical stimulation of parasympathetic nerves innervating the sinus node has been shown to decrease sinus rate. We investigated whether intravascular parasympathetic cardiac nerve stimulation (IPS) can be achieved over a relatively long-term period to slow the supraventricular rate. METHODS AND RESULTS: Fifteen dogs were investigated. IPS was performed ...
Tieleman R G - - 1999
BACKGROUND: Atrial fibrillation (AF) induces electrical remodeling, which is thought to be responsible for the low success rate of antiarrhythmic treatment in AF of longer duration. Electrical remodeling seems to be related to tachycardia-induced intracellular calcium overload. Due to its vagomimetic action, digoxin is widely used to control the ventricular ...
Desai S A - - 1999
BACKGROUND: The global T-inversion (GTI) electrocardiogram (ECG) is strikingly abnormal with major QTc prolongation, but with a surprisingly good prognosis by Kaplan-Meier curve. This contrasts with most significant QTc prolongations. HYPOTHESIS: This study was undertaken to ascertain QT interval dispersion (QTd) in global T wave inversion, a clinically benign long ...
Schwaab B - - 1999
AV conduction with atrial rate adaptive pacing (AAIR) during exercise was investigated in 43 patients (28 men, 15 female, mean age 68 +/- 7 years) who were paced and medicated with antiarrhythmic drugs for the bradycardia tachycardia syndrome (BTS). Patients were included if they had no second- or third-degree AV ...
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