Search Results
Results 651 - 700 of 1164
< 9 10 11 12 13 14 15 16 17 18 19 >
Haywood G A - - 1993
OBJECTIVE: To test the hypotheses that adaptive rate atrial (AAIR) pacing: significantly increases maximal exercise capacity, and results in significant suppression of supraventricular and ventricular arrhythmia compared with fixed rate atrial (AAI) pacing. DESIGN: Prospective, randomised, single blind, crossover study with maximal treadmill exercise testing and 24 hour ambulatory electrocardiographic ...
Bastianon V - - 1993
The incidence of sudden death in children with congenital aortic stenosis (CAS) varies between 4 and 20%. In several syndromes sudden death is associated with a long QT interval in the electrocardiogram (ECG). The aim of the study was to evaluate the cardiac repolarization in CAS during stress. We included ...
Stark G - - 1993
Negative chronotropic and dromotropic effects of adenosine seem to be responsible for its antiarrhythmic action on supraventricular tachyarrhythmias. To further characterize the effects of adenosine on supraventricular arrhythmias heart rate, conduction, refractoriness, the time to steady-state of AV-nodal conduction slowing and of sinus rate reduction were evaluated. Changes of heart ...
Singer D E - - 1992
Recent randomized trials have consistently demonstrated the marked efficacy of warfarin in reducing the risk of stroke caused by nonrheumatic atrial fibrillation. These trials have provided conflicting evidence on the effect of aspirin. We report the aspirin analysis from the BAATAF study, a trial in which control patients could choose ...
Oreto G - - 1992
Sustained monomorphic ventricular tachycardia is usually regular; that is, it is associated with constant R-R intervals. In several cases, however, the cycles of ventricular tachycardia are more or less variable. Fifty-four cases of sustained monomorphic ventricular tachycardia were evaluated in order to assess whether tachycardia was regular. Nine cases were ...
Kay G N - - 1992
OBJECTIVES: The aim of this study was to develop a technique for quantitating chronotropic response. BACKGROUND: Although the importance of chronotropic response for optimizing cardiac output during exercise is widely recognized, methods for quantitating the rate-modulating behavior of permanent pacemakers have not been developed. For a method of quantitating chronotropic ...
Erdelitsch-Reiser E - - 1992
An accelerometer-based rate adaptive generator (EXCEL VR) has been introduced. A preclinical group of 22 subjects with strap-on devices was observed and reported. A clinical protocol including observation of rate adaptive response to typical daily activities and incremental exercise on a treadmill was administered in seven implanted patients. Indications for ...
Linde-Edelstam C M - - 1992
The relative importance of atrial systole on left ventricular filling was investigated at rest and during exercise in 25 patients with dual chamber pacemakers. The mean blood flow velocity over the mitral valve, the velocities of the rapid filling phase (E), the active filling phase (A), and the E/A ratio ...
Mahaux V - - 1992
The usefulness of sensor data storage for rate response simulation was evaluated using a new dual chamber rate modulated pacemaker sensitive to acceleration forces (Relay 294-03 [Intermedics Inc.]). The pacemaker can store the sensor output during routine exercise and those values can be used to simulate rate profiles for other ...
Pichlmaier A M - - 1992
A multicenter clinical study is presented, which focuses on the reestablishment of closed loop cardiac control in patients with chronotropic insufficiency. Using the information about sympathetic tone contained in the myocardial contractility, it is possible to reconnect the heart rate to the physiological control mechanisms. Intracardiac impedance is measured with ...
Kubac G - - 1992
OBJECTIVE: To measure exercise duration (which frequently is diminished by atrial fibrillation) and to compare the gain in exercise duration achieved by heart rate control with the gain after cardioversion. METHODS AND RESULTS: Eighteen patients (10 with structural heart condition and eight with lone atrial fibrillation) did the treadmill exercise ...
Theodorakis G N - - 1992
The purpose of the study was to assess at rest and during exercise total sympathetic activity, as expressed by plasma cyclic AMP (cAMP) blood levels and sinus node activity (SNA), as well as atrial natriuretic factor (ANF) blood levels in VVI and DDD pacing with long and short atrioventricular delays ...
Lau C P - - 1992
Although ventricular rate adaptive pacing (VVIR) improves exercise capacity and cardiac output compared to constant rate ventricular pacing (VVI), this pacing mode does not provide benefit of atrioventricular (AV) synchrony. We evaluated the use of a custom-built VDDR pacing system using a single pass, ventricular lead, which detects endocavity P ...
Mahaux V - - 1992
A sensor driven algorithm limiting ventricular pacing rate during supraventricular tachycardia (SVT) is included in a dual chamber rate modulated pacemaker sensitive to acceleration forces (Relay, 294-03, Intermedics Inc.). According to the intensity of concomitant exercise, the ventricular pacing rate is limited either to the programmed maximum pacing rate (MPR) ...
Kamke W - - 1992
To facilitate follow-up, modern dual chamber pacemakers provide a variety of diagnostic features like ECG interpretation channels and intracardiac electrograms. For evaluation of the sensing performance at rest and during exercise, for assessment of the presence of crosstalk, and for measurement of the retrograde conduction time, dual chamber triggered pacing, ...
Wilkoff B L - - 1992
Cardiac chronotropic analysis has only begun to develop into a clinically relevant science. In the past, formal exercise testing was usually relegated to the assessment of ischemia or cardiac rehabilitation. The establishment of rate-responsive pacemakers as a potentially effective treatment for chronotropic incompetence forced the definition of cardiac chronotropism and ...
Lemke B - - 1992
Whether heart rate or AV synchrony is the most important factor for an increase in aerobic capacity was evaluated in a comparative study between sinus bradycardia, VVIR, DDD, and DDDR stimulation. Sixteen patients (mean age 67 years) with chronotropic incompetence and implanted DDDR pacemaker (Telectronics META 1250) were randomly studied ...
Borst U - - 1992
A new accelerometer-based adaptive rate pacemaker (EXCEL VR) was evaluated to investigate its behavior at nominal settings during treadmill exercise testing and postural changes. Eight patients with sinus rhythm were selected to compare intrinsic heart rate to sensor mediated rate. Throughout exercise treadmill testing, changes in the sensor mediated rate ...
Schaldach M - - 1992
Modern pacemaker technology renders possible the adaptation of pacing rate to hemodynamic requirements. The most ambitious approach aims at restoration of the physiological closed-loop system by utilizing the information supplied by the autonomic nervous system (ANS) and extracted from myocardial contractile performance. Measurement is accomplished by the impedance method using ...
Murray K D - - 1992
The native atria remains intact after total artificial heart (TAH) implantation. The electrical activity of the recipient's atria can be recorded from wires placed during TAH implantation. Regulating TAH heart rate by coupling it with native atrial activity has the potential for a more physiologically responsive TAH. The reactivity of ...
Zarling J - - 1992
Seven patients with previously implanted accelerometer-based DDDR pacemakers had an identically programmed external pacemaker taped onto their chest. Both units underwent a simultaneous test to set the sensitivity of the accelerometer. The units were then programmed to record the pacing rates for a 15-minute period. The patients underwent an exercise ...
Katritsis D - - 1992
Many types of artificial sensors for adaptive-rate pacing have appeared but as yet there is no single sensor that properly reflects metabolic demand under all circumstances. Several other types of sensors are currently evaluated. Combinations of different sensors in a single unit are very promising. At present, however, the only ...
van Gelder B M - - 1992
Wenckebach behavior of DDD pacemakers occurring when the P-P interval varies between the programmed upper rate interval and the total atrial refractory period is symmetrical in a sense that the pacemaker response during atrial rate acceleration is similar to the pacemaker response during atrial rate deceleration. This phenomenon can be ...
Capucci A A Institute of Cardiovascular Diseases, University of Bologna, - - 1992
In eight patients (age 62 +/- 6 years) a DDDR pacemaker was implanted for sick sinus syndrome (three cases) or second- and third-degree AV block (five cases). In five subjects chronotropic incompetence (maximal heart rate on effort < 110 beats/min) was present before implantation. One month after implantation the patients ...
Auricchio A - - 1992
In 34 patients with a symptomatic accessory atrioventricular connection the reversible protective effect of orally administered flecainide (300 mg/day) and of propafenone (900 mg/day) in control of ventricular response during atrial fibrillation by exercise was assessed. The study consisted of three sections of 1 week each: an initial treatment phase ...
Tani M - - 1992
To identify the effect of chronotropic responsive cardiac pacing on the ventilatory response to exercise, ten selected patients with complete atrioventricular block underwent paired cardiopulmonary exercise tests in fixed rate ventricular (VVI) and dual chamber (DDD) or rate responsive ventricular (VVIR) pacing modes. Compared to VVI pacing, DDD or VVIR ...
Coghlan J G - - 1992
The QT responses to exercise during ventricular pacing were evaluated in 12 patients in whom permanent pacemakers were implanted for complete heart block. The initial response of the QT to exercise was a paradoxical lengthening during the first minute of exercise (mean 4.8 ms P < 0.01). Thereafter, the QT ...
Weinhold C - - 1992
Rate-response dual-chamber pacing combines the advantages of atrio-ventricular synchrony and rate adaptation in patients suffering from binodal disease. However, it is not known if patients really benefit from the additional rate response under exercise conditions. Therefore, 15 patients suffering from binodal disease received rate-responsive dual-chamber pacemakers. 1, 3, and 6 ...
Abildskov J A - - 1992
In this study, the spatial pattern of refractoriness and its effects on propagation of excitation during premature responses and tachycardia have been investigated using a computer model. The model simulated propagation, cycle length-dependent refractoriness, and slow propagation during the relative refractory period. Findings showed slow propagation near the origin of ...
Reig J - - 1992
A 69-year-old woman was referred for asthenia and dizziness when walking in the last two months. No clinical abnormalities were found, and sinus rhythm was present when lying down. On orthostatism and walking, advanced AV block developed. Atropine and isoproterenol ameliorated the AV conduction abnormality, suggesting a nodal block. The ...
Ehlert F A - - 1992
The ability to predict the RR-QT relation over a range of heart rates was evaluated in 10 patients with atrial fibrillation (AF) and in 10 control subjects in sinus rhythm. The data from each subject were fitted by regression into 3 QT prediction formulas (the square root formula of Bazett, ...
Chimienti M - - 1992
In order to evaluate the effects of increases of sympathetic tone in ventricular response during atrial fibrillation and in the relationship between the accessory pathway effective refractory period (ERP) and ventricular rate during atrial fibrillation, 20 male subjects, aged 19 +/- 6 years, were studied electrophysiologically in basal conditions, after ...
Bellamy C M - - 1992
Two new generation rate adaptive pacemakers, the Rhythmyx (Vitatron) using the evoked QT interval and the Legend (Medtronic) using vibration as indicators of metabolic demand, were compared for rate adaptive characteristics during different forms of exercise. While both showed improvements over previous generation pacemakers, they still show deficiencies in some ...
Martin D - - 1992
The present generation implantable defibrillator introduced on-line event markers that can be used to evaluate tachycardia detection in the electrophysiological testing mode. These markers were used to assess the appropriateness of programming the morphology criterion for detection of ventricular tachycardia. Twenty-one consecutive patients (19 men, 2 women) performed 29 bicycle ...
Matthys D - - 1992
Impairment of sinus rhythm has been reported after the Mustard procedure for complete transposition. We observed two patients who developed severe bradycardia during or after exercise. The first had a 2.8 s sinus pause in the recovery period, the second had a drop in heart rate during exercise. Both eventually ...
Lascault G - - 1992
The non-invasive haemodynamic comparisons of DDD and 'VVI-R like' pacing at rest and during moderate exercise by echo Doppler are reported. Twelve patients (six males, six females, mean age 48.2 years) with a dual chamber pacemaker were submitted to a series of two exercise tests in a semi-supine position, the ...
Kühlkamp V - - 1992
The electrophysiologic effects of pentisomide were investigated after intravenous (5 mg/kg) and oral (900-1200 mg three times a day) application in 9 patients with drug refractory atrioventricular nodal tachycardia and 6 patients with orthodromic atrioventricular re-entrant tachycardia. Pentisomide did not change sinus cycle length, effective refractory period of the right ...
Maity A K - - 1992
Sequential cardiac chamber activation and chronotropic response are amongst the important determinants of cardiac performance. This study compared VVIR mode with DDD and VVI mode to assess the contribution of these two factors in the determination of cardiac performance during exercise. Ten patients with a mean age of 68 +/- ...
Wang H Z HZ Department of Pharmacology, State University of New York Health Science Center, Syracuse - - 1992
Numerous two-cell voltage-clamp studies have concluded that the electrical conductance of mammalian cardiac gap junctions is not modulated by the transjunctional voltage (Vj) profile, although gap junction channels between low conductance pairs of neonatal rat ventricular myocytes are reported to exhibit Vj-dependent behavior. In this study, the dependence of macroscopic ...
Ruiter J H - - 1992
In the Precept pacing system, the right ventricular intracardiac impedance waveform is used to evaluate either of two indicators of metabolic demand relative right ventricular stroke volume and preejection interval (PEI). PEI is known to reliably parallel contractility changes, which is reflective of physical and emotional stress. The stability and ...
Linde-Edelstam C - - 1992
To assess the variation in paced rate during everyday activity and the importance of atrioventricular synchronization (AV synchrony) for submaximal exercise tolerance, atrial synchronous (DDD) and activity rate modulated ventricular (VVI,R) pacing were compared in 17 patients with high degree AV block. The patients were randomly assigned to either mode ...
O'Hara G G Department of Medicine, Montreal Heart Institute, Quebec, - - 1992
Flecainide is effective against certain supraventricular arrhythmias (atrial fibrillation and atrioventricular [AV] node reentrant tachycardia), but its mechanisms of action are unknown. Previous in vitro work suggests that flecainide attenuates rate-dependent action potential duration shortening, producing tachycardia-dependent prolongation of the refractory period. This study was designed to assess whether similar ...
Asano Y - - 1992
In an effort to further clarify the mechanism of termination and perpetuation of atrial fibrillation (AF), the intraatrial potentials during AF induced by programmable electrical stimulation were analyzed using the concept of wavelength which represents the size of a microreentrant circuit. Thirty patients with inducible AF were divided into 2 ...
Blanc J J - - 1992
Dual chamber pacemakers were implanted in nine patients with permanent second or third degree AV block (eight had complete retrograde block). Two identical exercise tests were performed after at least 1 month after implantation. During the first test (T1) the pacemaker was programmed to the DDD mode and heart rates ...
Sulke A N - - 1992
Modern DDDR (dual chamber universal, rate responsive) pacemakers are complex, hugely capable devices incorporating new features that theoretically should enhance haemodynamics and therefore quality of life. Ten patients (mean age 48 years) with chronotropic incompetence and high grade A-V block had activity sensing DDDR devices implanted and underwent a randomized ...
Gough S C - - 1992
The effect of heart rate on plasma fibrinolytic activity was investigated in nine patients with dual chamber cardiac pacemakers before and after 10 min of stimulated tachycardia to 123 beats/min. The results were compared to seven volunteers who performed submaximal exercise to 90% target heart rate and to five of ...
Vassalle M - - 1992
OBJECTIVE: The pacemaker current in cardiac Purkinje fibres has been attributed to either a decrease in potassium conductance or an increase in a non-specific (Na-K) conductance. The former mechanism would be associated with an increase in membrane resistance (Rm) and the latter with a decrease in Rm. The aim of ...
Lau C P - - 1992
The rate adaptive characteristics and pacemaker mediated tachycardia protection algorithm of an accelerometer based DDDR pacemaker were evaluated in 11 patients with bradycardia (seven atrioventricular block, four sick sinus syndrome). Rate adaptive programming was effected by collecting the acceleration level during a 3-minute moderate exercise ("tailoring" of sensor). In comparison ...
Lee R J - - 1992
The cycle length dependence of the action potential duration and the effective refractory period of the right ventricular endocardium were investigated in 24 patients undergoing electrophysiologic studies for suspected ventricular tachycardia. The action potential duration at 90% repolarization and the effective refractory period at twice diastolic threshold strength were measured ...
Tobé T J - - 1992
The purpose of this study was to determine the incidence of late potentials and their relation to QT prolongation in a family with a high incidence of sudden death during sleep at a young age and bradycardia-dependent QT prolongation (n = 9) and to compare the findings with those in ...
< 9 10 11 12 13 14 15 16 17 18 19 >