Search results for "Pacing"
showing 10 items of 68 documents
Ventricular paired pacing to control intractable junctional tachycardia following open heart surgery in a child.
1989
A 5-month-old girl presented postoperatively with an atrioventricular (A-V) junctional tachycardia at a rate of 245/min following surgical repair of tetralogy of Fallot. The systolic blood pressure dropped to 60 mmHg with this rapid heart rate, and the infant became shocked. Drugs and overdrive pacing were ineffective in suppressing the A-V junctional tachycardia and in improving cardiac output. Ventricular paired pacing was used successfully to halve the mechanically effective ventricular rate and to restore cardiac output. When ventricular paired pacing was stopped after 12 h, the spontaneous rhythm was an atrial rhythm with 1-1 A-V conduction. The patient was discharged in sinus rhythm o…
A simple method for preoperative assessment of the best fitting electrode length in single lead VDD pacing.
1996
For single lead VDD pacing, electrodes with various distances between the lead tip and the floating atrial dipole (AV distance) are available. Using different AV distances allows positioning of the atrial dipole in the mid- to high right atrium, regardless of the size of the right heart. In this position, reliable atrial sensing and rejection of ventricular far-field potentials can be expected. A simple test for the preoperative assessment of the best fitting AV distance in the individual patient was tested. We studied 24 consecutive patients prior to implantation of a VDD pacemaker. With the patient in supine position, a test electrode with an AV distance of 13 cm was taped onto the thorax…
Dual-Diameter Laterals in Center-Pivot Irrigation System
2022
Design strategies to enhance modern irrigation practices, reduce energy consumption, and improve water use efficiency and crop yields are fundamental for sustainability. Concerning Center-Pivot Irrigation Systems, different design procedures aimed at optimizing water use efficiency have been proposed. Recently, following a gradually decreasing sprinkler spacing along the pivot lateral with constant diameter and sprinkler flow rate, a new design method providing a uniform water application rate has been introduced. However, no suggestions were given to design multiple-diameter laterals characterized by different values of the inside pipe diameter. In this paper, first the previous design pro…
Wider Letter-Spacing Facilitates Word Processing but Impairs Reading Rates of Fast Readers
2020
Previous reports of improved oral reading performance for dyslexic children but not for regular readers when between-letter spacing was enlarged led to the proposal of a dyslexia-specific deficit in visual crowding. However, it is in this context also critical to understand how letter spacing affects visual word recognition and reading in unimpaired readers. Adopting an individual differences approach, the present study, accordingly, examined whether wider letter spacing improves reading performance also for non-impaired adults during silent reading and whether there is an association between letter spacing and crowding sensitivity. We report eye movement data of 24 German students who sile…
Management of a patient with multiple device replacements and extractions: When the leadless pacemaker is a viable solution
2022
Leadless pacemaker (LPs) is a safe device and the implantation rates of this device is increasing. The device extraction and replacement are today a challenging procedures especially in case of infections, fragile and older patients or in unfavorable venous anatomy; LPs can be a valid alternative strategy in these cases. We report a case of management of a patient with multiple previous device replacements and extractions, with malfunction of transvenous pacemaker and with a fibrous membrane between the walls of the ventricular lead and the superior vena cava (SVC), who underwent a successful LP implantation.
Dofetilide effects on the inhibition by trains of subthreshold conditioning stimuli.
2004
We investigated the electrophysiological actions of dofetilide upon the ventricular myocardium to determine whether the drug modifies the inhibitory effects of subthreshold stimuli trains upon ventricular refractoriness. In nine Langendorff perfused rabbit hearts, ventricular epicardial electrodes were used to determine the following parameters at baseline and during dofetilide perfusion (0.5 micromolar): effective (ERP) and functional (FRP) refractory periods, conduction velocity (CV), wavelength (WL), and ERP prolongation (inhibitory effect) induced by subthreshold stimuli trains (STr) at pulse frequencies of 100, 300, and 600 Hz. Dofetilide significantly prolongs ventricular refractorine…
The Role of Cardiac Pacing in Heart Block Complicating Acute Myocardial Infarction
1983
The organization of the Coronary Care Unit and the use of electrocardiographic monitoring have allowed a re-evaluation of the incidence of the atrioventricular conduction disturbances in acute myocardial infarction.
Are double potentials markers of a specific zone of the atrioventricular junction in the isolated rabbit heart?
1997
A study is made of the characteristics of the atrial potentials recorded in the Koch triangle and its proximity, their variations on modifying the site of cardiac pacing, and their usefulness as markers of a distinct zone of the AV junction. In 12 isolated and perfused rabbit heart preparations an analysis was made of the endocardial atrial electrograms recorded with a multiple electrode positioned in the AV junction. The electrograms were obtained during spontaneous rhythm and on pacing at the crista terminalis (CT), interatrial septum (IAS), left atrium, and right ventricle. Double potentials were frequently obtained. On pacing at the CT, high-low double potentials (DP [H-L]) were more fr…
Subclinical atrial fibrillation: how hard should we look?
2012
More than three decades ago, an analysis from the Framingham Heart Study revealed that atrial fibrillation (AF) increases the risk of stroke by a factor of five in non-rheumatic AF and by a factor of 17 in rheumatic AF.1 Since then, it has convincingly been shown that anticoagulation is one of the most effective secondary stroke prophylactic treatment options, which reduces the risk of stroke by 2/3,2 even in an older population.3 AF may occur in different types and in an individual patient often starts with paroxysmal AF, but later becomes persistent or permanent AF.4 Interestingly, the risk of stroke or systemic embolism is influenced by cardiovascular risk factors such as hypertension, d…
Hemodynamic Effects of Ventricular Pacing
1985
Fixed rate ventricular pacing is used in most cases of implanted pacemakers. It does not usually create considerable hemodynamic problems, as the heart, by its adaptation mechanism, is capable of varying its pump performance to meet the metabolic needs[1,3].