The Experts below are selected from a list of 84 Experts worldwide ranked by ideXlab platform

Azadeh Davoodi - One of the best experts on this subject based on the ideXlab platform.

  • multi mode trace signal selection for post silicon debug
    Asia and South Pacific Design Automation Conference, 2014
    Co-Authors: Min Li, Azadeh Davoodi
    Abstract:

    Trace buffers are used during post-silicon debug to increase the visibility to the internal signals of a chip via online tracing of a few state elements within a Capture Window. Due to the small bandwidth of the trace buffer, only a few state elements can be selected or tracing in order to restore the states of the remaining state elements as many as possible. In this work, we show that the quality of restoration corresponding to a set of trace signals selected for a single operating mode, may significantly degrade over the remaining operating modes of a design; an operating mode refers to specific values taken by control signals such as signals for mode selection and scan enable. This is the first work to study the multi-mode trace signal selection problem in order to maximize the restoration over all the operating modes of a design. We propose algorithmic strategies for this problem as well as a procedure to reduce the number of modes by merging the ones with “similar” restoration maps; merging improves the runtime scalability of our multi-mode trace selection algorithm with increase in the number of modes, without much loss in the solution quality.

  • ASP-DAC - Multi-mode trace signal selection for post-silicon debug
    2014 19th Asia and South Pacific Design Automation Conference (ASP-DAC), 2014
    Co-Authors: Azadeh Davoodi
    Abstract:

    Trace buffers are used during post-silicon debug to increase the visibility to the internal signals of a chip via online tracing of a few state elements within a Capture Window. Due to the small bandwidth of the trace buffer, only a few state elements can be selected or tracing in order to restore the states of the remaining state elements as many as possible. In this work, we show that the quality of restoration corresponding to a set of trace signals selected for a single operating mode, may significantly degrade over the remaining operating modes of a design; an operating mode refers to specific values taken by control signals such as signals for mode selection and scan enable. This is the first work to study the multi-mode trace signal selection problem in order to maximize the restoration over all the operating modes of a design. We propose algorithmic strategies for this problem as well as a procedure to reduce the number of modes by merging the ones with “similar” restoration maps; merging improves the runtime scalability of our multi-mode trace selection algorithm with increase in the number of modes, without much loss in the solution quality.

Giovanni Quinto Villani - One of the best experts on this subject based on the ideXlab platform.

  • Capture Window in human atrial fibrillation: evidence of an excitable gap.
    Journal of cardiovascular electrophysiology, 1999
    Co-Authors: Alessandro Capucci, Flavia Ravelli, Giandomenico Nollo, A.s. Montenero, Mauro Biffi, Giovanni Quinto Villani
    Abstract:

    Capture Window in Human AF. Introduction: Local Capture of atrial fibrillation (AF) was shown in animal experiments for a wide range of pacing rates, thus demonstrating the existence of an excitable gap. The aim of this study was to assess the existence of an excitable gap in human AF by studying the mechanism of local control and acceleration of AF over a wide range of pacing rates and by evaluating the time Window of Capture. Methods and Results: Recording and stimulation of electrical activity in the right atrium during AF was performed by a monophasic action potential (MAP) contact electrode catheter in 17 patients with lone AF during electrophysiologic study. Stimulation was started at pacing intervals close to the mean AF interval, and the time Window of Capture was estimated by lengthening or shortening the pacing interval until Capture was lost. Pacing intervals shorter than the minimum cycle length for Capture were also tested. Beat-to-beat measurements of AF intervals during pacing were performed. Atrial MAP signal showed rapid irregular activity with an average AF interval of 151.3 ± 16.1 msec and SD of 21.3 ± 5.2 msec. Rapid pacing with a cycle length slightly shorter or longer than the mean AF interval resulted in local Capture of AF. The width of time Window of Capture ranged from 22 to 36 msec, with a mean value of 28.8 ± 4.9 msec. The average minimum pacing interval of stable Capture was 129.2 ± 19.5 msec, while the maximum was 158.1 ± 18.7 msec, corresponding to 85% and 104% of mean AF cycle length, respectively. Pacing too rapidly resulted in a transient acceleration of AF, with an average shortening of fibrillation interval from 149.8 ± 16.6 to 123.2 ± 15.1 msec (P < 0.01). Conclusion: Local Capture is feasible during AF in humans over a wide range of pacing rates, indicating the possibility of regional control of the fibrillatory process. This result demonstrates the presence of an excitable gap during AF in human atria.

Jean-marc Vesin - One of the best experts on this subject based on the ideXlab platform.

  • Impact of Conduction Velocity on Local Capture of Atrial Fibrillation Induced by Rapid Pacing
    The Cardiology, 2015
    Co-Authors: Nathalie Virag, Adrian Luca, Kallmyer Todd, Alexandru Rusu, Jean-marc Vesin
    Abstract:

    Objectives: Rapid pacing of atrial fibrillation (AF) can induce local atrial Capture. The present model-based study investigated the impact of atrial tissue conduction velocity on AF Capture ability during rapid septal pacing. Methods: The AF model combined a membrane kinetics model with geometry based on computed tomography of AF patients. Conduction velocity was varied ±20% over a baseline AF model based on multiple reentrant wavelets. Rapid pacing of AF was applied from the septum for 50s with pacing cycle length (PCL) computed as percent of mean AFCL. Analysis of 24 electrode pairs evenly distributed on the atrial surface yielded percentage of Captured tissue (CL within ±5% of PCL). Capture Window was the range of PCL with Capture > 50%. Reentrant wavelets quantity (#W) was computed before and during pacing. Optimal PCL was leading to the highest Capture. Results were averaged on 10 AF simulations. Results: AFCL did not change significantly with conduction velocity, and optimal PCL was comparable for the 3 velocity values. An increase/decrease in velocity reduced/extended the Capture Window. The maximum Capture was obtained with a decreased conduction velocity even if #W was higher prior to pacing. Conclusions: Changes in atrial tissue conduction properties produced significant differences in rapid pacing outcomes, suggesting that different types of AF may respond differently to therapeutic pacing. Optimal Capture parameters depended on AF dynamics but not AFCL.

  • Optimizing Local Capture of Atrial Fibrillation by Rapid Pacing: Study of the Influence of Tissue Dynamics
    Annals of Biomedical Engineering, 2010
    Co-Authors: Laurent Uldry, Nathalie Virag, Vincent Jacquemet, Jean-marc Vesin, Lukas Kappenberger
    Abstract:

    While successful termination by pacing of organized atrial tachycardias has been observed in patients, rapid pacing of AF can induce a local Capture of the atrial tissue but in general no termination. The purpose of this study was to perform a systematic evaluation of the ability to Capture AF by rapid pacing in a biophysical model of the atria with different dynamics in terms of conduction velocity (CV) and action potential duration (APD). Rapid pacing was applied during 30 s at five locations on the atria, for pacing cycle lengths in the range 60–110% of the mean AF cycle length (AFCL_mean). Local AF Capture could be achieved using rapid pacing at pacing sites located distal to major anatomical obstacles. Optimal pacing cycle lengths were found in the range 74–80% AFCL_mean (Capture Window width: 14.6 ± 3% AFCL_mean). An increase/decrease in CV or APD led to a significant shrinking/stretching of the Capture Window. Capture did not depend on AFCL, but did depend on the atrial substrate as characterized by an estimate of its wavelength, a better Capture being achieved at shorter wavelengths. This model-based study suggests that a proper selection of the pacing site and cycle length can influence local Capture results and that atrial tissue properties (CV and APD) are determinants of the response to rapid pacing.

Natalia A. Trayanova - One of the best experts on this subject based on the ideXlab platform.

  • Mechanisms of Myocardial Capture and Temporal Excitable Gap During Spiral Wave Reentry in a Bidomain Model
    Circulation, 2004
    Co-Authors: Takashi Ashihara, Tsunetoyo Namba, Takanori Ikeda, Makoto Ito, Kazuo Nakazawa, Natalia A. Trayanova
    Abstract:

    Background— Recent studies have demonstrated that regional Capture during cardiac fibrillation is associated with an elevated Capture threshold. It is typically assumed that the temporal excitable gap (Capture Window) during fibrillation reflects the size of the spatial excitable gap (excitable tissue between fibrillation waves). Because Capture threshold is high, virtual electrode polarization is expected to be involved in the process. However, little is known about the underlying mechanisms of myocardial Capture during fibrillation. Methods and Results— To clarify these issues, we conducted altogether 3168 simulations of single spiral wave Capture in a bidomain sheet. Unipolar stimuli of strengths 4, 8, 16, and 24 mA and 2-ms duration were delivered at 99 locations in the sheet. We found that cathode-break rather than cathode-make excitation was the dominant mechanism of myocardial Capture. When the stimulation site was located diagonally with respect to the core (upper left or lower right if the spiral...

Nathalie Virag - One of the best experts on this subject based on the ideXlab platform.

  • Impact of Conduction Velocity on Local Capture of Atrial Fibrillation Induced by Rapid Pacing
    The Cardiology, 2015
    Co-Authors: Nathalie Virag, Adrian Luca, Kallmyer Todd, Alexandru Rusu, Jean-marc Vesin
    Abstract:

    Objectives: Rapid pacing of atrial fibrillation (AF) can induce local atrial Capture. The present model-based study investigated the impact of atrial tissue conduction velocity on AF Capture ability during rapid septal pacing. Methods: The AF model combined a membrane kinetics model with geometry based on computed tomography of AF patients. Conduction velocity was varied ±20% over a baseline AF model based on multiple reentrant wavelets. Rapid pacing of AF was applied from the septum for 50s with pacing cycle length (PCL) computed as percent of mean AFCL. Analysis of 24 electrode pairs evenly distributed on the atrial surface yielded percentage of Captured tissue (CL within ±5% of PCL). Capture Window was the range of PCL with Capture > 50%. Reentrant wavelets quantity (#W) was computed before and during pacing. Optimal PCL was leading to the highest Capture. Results were averaged on 10 AF simulations. Results: AFCL did not change significantly with conduction velocity, and optimal PCL was comparable for the 3 velocity values. An increase/decrease in velocity reduced/extended the Capture Window. The maximum Capture was obtained with a decreased conduction velocity even if #W was higher prior to pacing. Conclusions: Changes in atrial tissue conduction properties produced significant differences in rapid pacing outcomes, suggesting that different types of AF may respond differently to therapeutic pacing. Optimal Capture parameters depended on AF dynamics but not AFCL.

  • Optimizing Local Capture of Atrial Fibrillation by Rapid Pacing: Study of the Influence of Tissue Dynamics
    Annals of Biomedical Engineering, 2010
    Co-Authors: Laurent Uldry, Nathalie Virag, Vincent Jacquemet, Jean-marc Vesin, Lukas Kappenberger
    Abstract:

    While successful termination by pacing of organized atrial tachycardias has been observed in patients, rapid pacing of AF can induce a local Capture of the atrial tissue but in general no termination. The purpose of this study was to perform a systematic evaluation of the ability to Capture AF by rapid pacing in a biophysical model of the atria with different dynamics in terms of conduction velocity (CV) and action potential duration (APD). Rapid pacing was applied during 30 s at five locations on the atria, for pacing cycle lengths in the range 60–110% of the mean AF cycle length (AFCL_mean). Local AF Capture could be achieved using rapid pacing at pacing sites located distal to major anatomical obstacles. Optimal pacing cycle lengths were found in the range 74–80% AFCL_mean (Capture Window width: 14.6 ± 3% AFCL_mean). An increase/decrease in CV or APD led to a significant shrinking/stretching of the Capture Window. Capture did not depend on AFCL, but did depend on the atrial substrate as characterized by an estimate of its wavelength, a better Capture being achieved at shorter wavelengths. This model-based study suggests that a proper selection of the pacing site and cycle length can influence local Capture results and that atrial tissue properties (CV and APD) are determinants of the response to rapid pacing.