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Mode Switching (mode + switching)
Selected AbstractsAutomatic Mode Switching of Implantable Pacemakers: II.PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 7 2002Clinical Performance of Current Algorithms, Their Programming LAU, C.-P., et al.: Automatic Mode Switching of Implantable Pacemakers: II. Clinical Performance of Current Algorithms and Their Programming. While the hemodynamic and clinical significance of automatic mode switching (AMS) in patients with pacemakers has been demonstrated, the clinical behavior of AMS algorithms differ widely according to the manufacturers and pacemaker models. In general, a "rate-cutoff" detection method of atrial tachyarrhythmias provides a rapid AMS onset and resynchronization to sinus rhythm at the termination of atrial tachyarrhythmias, but may cause intermittent oscillations between the atrial tracking and AMS mode. This can be minimized with a "counter" of total number of high rate events before the AMS occurs. The use of a "running average" algorithm results in more stable rate control during AMS by reducing the incidence of oscillations, but at the expense of delayed AMS onset and resynchronization to sinus rhythm. Algorithms may be combined to fine tune the AMS response and to avoid rapid fluctuation in pacing rate. Appropriate programming of atrial sensitivity, and the avoidance of ventriculoatrial cross-talk are essential for optimal AMS performance. [source] Automatic Mode Switching of Implantable Pacemakers: I. Principles of Instrumentation, Clinical, and Hemodynamic ConsiderationsPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 6 2002CHU-PAK LAU LAU, C.-P., et al.: Automatic Mode Switching of Implantable Pacemakers: I. Principles of Instrumentation, Clinical, and Hemodynamic Considerations. Automatic mode switching (AMS) is now a programmable function in most contemporary dual chamber pacemakers. Atrial tachyarrhythmias are detected when the sensed atrial rate exceeds a "rate-cutoff,""running average,""sensor-based physiological" rate, or using "complex" detection algorithms. AMS algorithms differ in their atrial tachyarrhythmia detection method, sensitivity, and specificity and, thus, respond differently to atrial tachyarrhythmia in terms of speed to the AMS onset, rate stability of the response, and speed to resynchronize to sinus rhythm. AMS is hemodynamically beneficial, and most patients with atrial tachyarrhythmias are symptomatically better with an AMS algorithm in their pacemakers. New diagnostic capabilities of pacemaker especially stored electrograms not only allow programming of the AMS function, but enable quantification of atrial fibrillation burden that facilitate clinical management of patients with implantable devices who have concomitant atrial tachyarrhythmia. [source] Incidence of Atrial Arrhythmias Detected by Permanent Pacemakers (PPM) Post-Pulmonary Vein Antrum Isolation (PVAI) for Atrial Fibrillation (AF): Correlation with Symptomatic RecurrenceJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 6 2007ATUL VERMA M.D. Background: Studies examining AF recurrences post-PVAI base recurrence on patient reporting of symptoms. However, whether asymptomatic recurrences are common is not well known. Objective: To assess the incidence of atrial tachycardia/fibrillation post-PVAI as detected by a PPM and whether these recurrences correlate to symptomatic recurrence. Methods: Eighty-six consecutive patients with symptomatic AF and PPMs with programmable mode-switch capability underwent PVAI. Mode switching was programmed post-PVAI to occur at an atrial-sensed rate of >170 bpm. Patients were followed with clinic visits, ECG, and PPM interrogation at 1, 3, 6, and 9 months post-PVAI. The number and duration of mode-switching episodes (MSEs) were recorded at each visit and is presented as median (interquartile range). Results: The patients (age 57 ± 8 years, EF 54 ± 10%) had paroxysmal (65%) and persistent (35%) AF pre-PVAI. Sensing, pacing, and lead function were normal for all PPMs at follow-up. Of the 86 patients, 20 (23%) had AF recurrence based on symptoms. All 20 of these patients had appropriate MSEs detected. Of the 66 patients without symptomatic recurrence, 21 (32%) had MSEs detected. In 19 of these patients, MSEs were few in number, compared with patients with symptomatic recurrence (16 [4,256] vs 401 [151,2,470], P < 0.01). The durations were all <60 seconds. All of these nonsustained MSEs occurred within the first 3 months post-PVAI, gradually decreasing over time. The other 2 of 21 remaining patients had numerous (1,343 [857,1,390]) and sustained (18 ± 12 minutes) MSEs that also persisted beyond 3 months (1 beyond 6 months). Therefore, the incidence of numerous, sustained MSEs in asymptomatic patients post-PVAI was 2 of 66 (3%). Conclusions: Detection of atrial tachyarrhythmias by a PPM occurred in 30% of patients without symptomatic AF recurrence. Most of these episodes were <60 seconds and waned within 3 months. Sustained, asymptomatic episodes were uncommon. [source] Automatic Mode Switching of Implantable Pacemakers: II.PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 7 2002Clinical Performance of Current Algorithms, Their Programming LAU, C.-P., et al.: Automatic Mode Switching of Implantable Pacemakers: II. Clinical Performance of Current Algorithms and Their Programming. While the hemodynamic and clinical significance of automatic mode switching (AMS) in patients with pacemakers has been demonstrated, the clinical behavior of AMS algorithms differ widely according to the manufacturers and pacemaker models. In general, a "rate-cutoff" detection method of atrial tachyarrhythmias provides a rapid AMS onset and resynchronization to sinus rhythm at the termination of atrial tachyarrhythmias, but may cause intermittent oscillations between the atrial tracking and AMS mode. This can be minimized with a "counter" of total number of high rate events before the AMS occurs. The use of a "running average" algorithm results in more stable rate control during AMS by reducing the incidence of oscillations, but at the expense of delayed AMS onset and resynchronization to sinus rhythm. Algorithms may be combined to fine tune the AMS response and to avoid rapid fluctuation in pacing rate. Appropriate programming of atrial sensitivity, and the avoidance of ventriculoatrial cross-talk are essential for optimal AMS performance. [source] Automatic Mode Switching of Implantable Pacemakers: I. Principles of Instrumentation, Clinical, and Hemodynamic ConsiderationsPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 6 2002CHU-PAK LAU LAU, C.-P., et al.: Automatic Mode Switching of Implantable Pacemakers: I. Principles of Instrumentation, Clinical, and Hemodynamic Considerations. Automatic mode switching (AMS) is now a programmable function in most contemporary dual chamber pacemakers. Atrial tachyarrhythmias are detected when the sensed atrial rate exceeds a "rate-cutoff,""running average,""sensor-based physiological" rate, or using "complex" detection algorithms. AMS algorithms differ in their atrial tachyarrhythmia detection method, sensitivity, and specificity and, thus, respond differently to atrial tachyarrhythmia in terms of speed to the AMS onset, rate stability of the response, and speed to resynchronize to sinus rhythm. AMS is hemodynamically beneficial, and most patients with atrial tachyarrhythmias are symptomatically better with an AMS algorithm in their pacemakers. New diagnostic capabilities of pacemaker especially stored electrograms not only allow programming of the AMS function, but enable quantification of atrial fibrillation burden that facilitate clinical management of patients with implantable devices who have concomitant atrial tachyarrhythmia. [source] High-throughput metabolic stability studies in drug discovery by orthogonal acceleration time-of-flight (OATOF) with analogue-to-digital signal capture (ADC)RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 12 2010David G. Temesi Screening assays capable of performing quantitative analysis on hundreds of compounds per week are used to measure metabolic stability during early drug discovery. Modern orthogonal acceleration time-of-flight (OATOF) mass spectrometers equipped with analogue-to-digital signal capture (ADC) now offer performance levels suitable for many applications normally supported by triple quadruple instruments operated in multiple reaction monitoring (MRM) mode. Herein the merits of MRM and OATOF with ADC detection are compared for more than 1000 compounds screened in rat and/or cryopreserved human hepatocytes over a period of 3 months. Statistical comparison of a structurally diverse subset indicated good agreement for the two detection methods. The overall success rate was higher using OATOF detection and data acquisition time was reduced by around 20%. Targeted metabolites of diazepam were detected in samples from a CLint determination performed at 1,µM. Data acquisition by positive and negative ion mode switching can be achieved on high-performance liquid chromatography (HPLC) peak widths as narrow as 0.2,min (at base), thus enabling a more comprehensive first pass analysis with fast HPLC gradients. Unfortunately, most existing OATOF instruments lack the software tools necessary to rapidly convert the huge amounts of raw data into quantified results. Software with functionality similar to open access triple quadrupole systems is needed for OATOF to truly compete in a high-throughput screening environment. Copyright © 2010 John Wiley & Sons, Ltd. [source] A combined ion source for fast switching between electrospray and matrix-assisted laser desorption/ionization in Fourier transform ion cyclotron resonance mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2002Gökhan Baykut A new ion source has been developed for Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) that enables quick changes between matrix-assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI) modes. When operating as an ESI source, the sample solution is sprayed through an angled nebulizer. The generated ions pass through a glass capillary followed by a skimmer and three sequential hexapole ion guides. Ions can be accumulated in the third hexapole (storage hexapole) before they are injected into the ICR trap. The second hexapole is mounted on a movable platform which also carries the MALDI sample plate. During the switch from ESI to MALDI, this platform moves the second hexapole out of the hexapole series and locates a MALDI sample plate with 384 sample positions into the area directly in front of the storage hexapole. The storage hexapole is in a medium pressure chamber (MPC) which has windows both for the incoming laser beam and for the observation optics, as well as a gas tube for pulsing collision gas into the chamber. During the MALDI operation the focused laser beam enters the MPC, passes between the hexapole rods and irradiates a MALDI sample on the target plate. The sample molecules are desorbed/ionized into the storage hexapole and simultaneously cooled by collisions with the pulsed gas. Ions desorbed from multiple laser shots can be accumulated in this hexapole before they are transferred to the ICR trap. With the combined ion source a computer-controlled switch between MALDI and ESI modes is possible in less than a minute, depending on the position of the MALDI target on the 384-spot plate. Immediate acquisition of mass spectra is possible after mode switching without the need for tuning or re-calibration. Copyright © 2002 John Wiley & Sons, Ltd. [source] | ||||||||||