The Experts below are selected from a list of 8706 Experts worldwide ranked by ideXlab platform

Raymond E. Ideker - One of the best experts on this subject based on the ideXlab platform.

  • Left Ventricular Apex Ablation Decreases the Upper Limit of Vulnerability
    Circulation, 2000
    Co-Authors: Nipon Chattipakorn, Parwis C. Fotuhi, Xiangsheng Zheng, Raymond E. Ideker
    Abstract:

    Background —After shocks with an ≈50% probability of success for the upper limit of vulnerability (ULV50) of strength, the first few activations appear focally on the epicardium at almost the same site at the left ventricular (LV) apex in both successful and failed induction of ventricular fibrillation (VF). We tested the hypothesis that subendocardial ablation at this early site would decrease the shock strength required for the ULV50. Methods and Results —Ten S1 stimuli were Delivered from the right ventricular apex at a 300-ms coupling interval in 5 pigs. Biphasic shocks were Delivered from right ventricular–superior vena cava electrodes after the last S1 stimulus. The ULV50 was determined using an up/down protocol with T-wave scanning. Radiofrequency ablation was performed endocardially at the apical LV. The ULV50 was determined again 30 minutes after ablation. To determine the importance of the ablation region, this protocol was repeated in another 5 pigs with ablation at the LV base. Delivered Voltage (401±60 versus 323±50 V) and energy (11±3 versus 7±2 J) for the ULV50 were significantly decreased after LV apex ablation by 19% and 34%, respectively. However, no difference existed in ULV50 before and after LV base ablation. Lesions at both the LV apex and base were subendocardial and ranged from 0.8 to 1.1 cm in diameter. Conclusions —Subendocardial ablation at the apical LV markedly decreases ULV50, which suggests that the activation originating from this postshock early site is responsible for VF initiation and that interventions to electrically silence this site can influence the outcome of VF induction by ULV shocks.

Ghassemi Amir - One of the best experts on this subject based on the ideXlab platform.

  • PEA Method Space Charge Measurement, modeling & measurement of applied pulsed-Voltage in different setups for MV mini-cable
    2020
    Co-Authors: Ghassemi Amir
    Abstract:

    Destructive consequences of trapped space charges within HVDC coaxial cable insulation, such as accelerated aging, degradation, and breakdown, are some of the most significant challenges that manufacturers and users usually come up with. Pulsed Electro-Acoustic (PEA) method is a widely-used method for space charge detection and measurement, in which the space charge profile is mapped through acoustic waves that are excited by applied pulsed-Voltage. There are a few practices for pulse application into PEA circuit. Pros and cons of the different injection practices have been remained unknown due to limited accessibility to the critical points like the core conductor. Digital twinning of the pulse injection setups can help us with simulating the key parameters, like Voltage and current, at the unreachable spots. The way how the circuit can be modeled, selecting adequate software and transmission line model, strengths and weaknesses of the injection practices and the changes required for possible optimization in the practices are challenging questions that need to be answered. This thesis develops frequency-dependent models for all the PEA injection setups that are usually deployed for Medium Voltage (MV) mini-cables geometry. It shows, through a validation process, that the PSCAD/EMTDC phase model can yield sufficiently accurate results with reference to the lab measurements. In the next stage, the questioned strengths and weaknesses of each original design setup are determined through a series of lab tests and computer-aided simulations, utilizing which the best setup is recognized. Seeking some approaches for further optimization of the setups is also another aim of this research. This thesis proves that the PSCAD/EMTDC phase model is capable to present acceptably exact digital twin for the circuits, despite having some limitations that will be explained. Operational versions of all setups, in which the fundamental problems are cleared up, will also be proposed in this thesis. Among all the setups, Core Pulse Injection (CPI) and Table Pulse Injection (TPI) practices offer the best non-optimized (original design) and optimized results, in terms of quality of the Delivered Voltage across the target dielectric respectively, while the original design of Double Side Pulse Injection (DSPI) and Single Side Pulse Injection (SSPI) seem to be unreliable due to severe oscillatory behaviors. Nevertheless, two modified versions for DSPI and SSPI show quality results

  • PEA Method Space Charge Measurement, modeling & measurement of applied pulsed-Voltage in different setups for MV mini-cable
    2020
    Co-Authors: Ghassemi Amir
    Abstract:

    Destructive consequences of trapped space charges within HVDC coaxial cable insulation, such as accelerated aging, degradation, and breakdown, are some of the most significant challenges that manufacturers and users usually come up with. Pulsed Electro-Acoustic (PEA) method is a widely-used method for space charge detection and measurement, in which the space charge profile is mapped through acoustic waves that are excited by applied pulsed-Voltage. There are a few practices for pulse application into PEA circuit. Pros and cons of the different injection practices have been remained unknown due to limited accessibility to the critical points like the core conductor. Modeling of the pulse injection setups can help us with simulating the essential parameters, like Voltage and current, at the unreachable spots. The way how the circuit can be modeled, selecting adequate software and transmission line model, strengths and weaknesses of the injection practices and the changes required for possible optimization in the practices are challenging questions that need to be answered. This thesis develops frequency-dependent models for all the PEA injection setups that are usually deployed for Medium Voltage (MV) mini-cables geometry. It shows, through a validationprocess, that PSCAD/EMTDC phase model can yield sufficiently accurate results with reference to the lab measurements. In the next stage, the questioned strengths and weaknesses of each original design setup are determined through a series of lab tests and computer-aided simulations by utilizing of which the best setup is recognized. Seeking some approaches for further optimization of the setups is also another aim of this research. This thesis proves that the PSCAD/EMTDC phase model is capable to present an acceptably exact model for the circuits, despite having some limitations that will be explained. Operationalversions of all setups, in which the fundamental problems are cleared up, will also be proposed in this thesis. Among all the setups, Core Pulse Injection (CPI) and Table Pulse Injection (TPI) practices offer the best non-optimized (original design) and optimized results, in terms of quality of the Delivered Voltage across the target dielectric respectively, while the original design of Double Side Pulse Injection (DSPI) and Single Side Pulse Injection (SSPI) seem to be unreliable due to severe oscillatory behaviors. Nevertheless, two modified versions for DSPI and SSPI show quality results.

Nipon Chattipakorn - One of the best experts on this subject based on the ideXlab platform.

  • Left Ventricular Apex Ablation Decreases the Upper Limit of Vulnerability
    Circulation, 2000
    Co-Authors: Nipon Chattipakorn, Parwis C. Fotuhi, Xiangsheng Zheng, Raymond E. Ideker
    Abstract:

    Background —After shocks with an ≈50% probability of success for the upper limit of vulnerability (ULV50) of strength, the first few activations appear focally on the epicardium at almost the same site at the left ventricular (LV) apex in both successful and failed induction of ventricular fibrillation (VF). We tested the hypothesis that subendocardial ablation at this early site would decrease the shock strength required for the ULV50. Methods and Results —Ten S1 stimuli were Delivered from the right ventricular apex at a 300-ms coupling interval in 5 pigs. Biphasic shocks were Delivered from right ventricular–superior vena cava electrodes after the last S1 stimulus. The ULV50 was determined using an up/down protocol with T-wave scanning. Radiofrequency ablation was performed endocardially at the apical LV. The ULV50 was determined again 30 minutes after ablation. To determine the importance of the ablation region, this protocol was repeated in another 5 pigs with ablation at the LV base. Delivered Voltage (401±60 versus 323±50 V) and energy (11±3 versus 7±2 J) for the ULV50 were significantly decreased after LV apex ablation by 19% and 34%, respectively. However, no difference existed in ULV50 before and after LV base ablation. Lesions at both the LV apex and base were subendocardial and ranged from 0.8 to 1.1 cm in diameter. Conclusions —Subendocardial ablation at the apical LV markedly decreases ULV50, which suggests that the activation originating from this postshock early site is responsible for VF initiation and that interventions to electrically silence this site can influence the outcome of VF induction by ULV shocks.

Parwis C. Fotuhi - One of the best experts on this subject based on the ideXlab platform.

  • Left Ventricular Apex Ablation Decreases the Upper Limit of Vulnerability
    Circulation, 2000
    Co-Authors: Nipon Chattipakorn, Parwis C. Fotuhi, Xiangsheng Zheng, Raymond E. Ideker
    Abstract:

    Background —After shocks with an ≈50% probability of success for the upper limit of vulnerability (ULV50) of strength, the first few activations appear focally on the epicardium at almost the same site at the left ventricular (LV) apex in both successful and failed induction of ventricular fibrillation (VF). We tested the hypothesis that subendocardial ablation at this early site would decrease the shock strength required for the ULV50. Methods and Results —Ten S1 stimuli were Delivered from the right ventricular apex at a 300-ms coupling interval in 5 pigs. Biphasic shocks were Delivered from right ventricular–superior vena cava electrodes after the last S1 stimulus. The ULV50 was determined using an up/down protocol with T-wave scanning. Radiofrequency ablation was performed endocardially at the apical LV. The ULV50 was determined again 30 minutes after ablation. To determine the importance of the ablation region, this protocol was repeated in another 5 pigs with ablation at the LV base. Delivered Voltage (401±60 versus 323±50 V) and energy (11±3 versus 7±2 J) for the ULV50 were significantly decreased after LV apex ablation by 19% and 34%, respectively. However, no difference existed in ULV50 before and after LV base ablation. Lesions at both the LV apex and base were subendocardial and ranged from 0.8 to 1.1 cm in diameter. Conclusions —Subendocardial ablation at the apical LV markedly decreases ULV50, which suggests that the activation originating from this postshock early site is responsible for VF initiation and that interventions to electrically silence this site can influence the outcome of VF induction by ULV shocks.

Xiangsheng Zheng - One of the best experts on this subject based on the ideXlab platform.

  • Left Ventricular Apex Ablation Decreases the Upper Limit of Vulnerability
    Circulation, 2000
    Co-Authors: Nipon Chattipakorn, Parwis C. Fotuhi, Xiangsheng Zheng, Raymond E. Ideker
    Abstract:

    Background —After shocks with an ≈50% probability of success for the upper limit of vulnerability (ULV50) of strength, the first few activations appear focally on the epicardium at almost the same site at the left ventricular (LV) apex in both successful and failed induction of ventricular fibrillation (VF). We tested the hypothesis that subendocardial ablation at this early site would decrease the shock strength required for the ULV50. Methods and Results —Ten S1 stimuli were Delivered from the right ventricular apex at a 300-ms coupling interval in 5 pigs. Biphasic shocks were Delivered from right ventricular–superior vena cava electrodes after the last S1 stimulus. The ULV50 was determined using an up/down protocol with T-wave scanning. Radiofrequency ablation was performed endocardially at the apical LV. The ULV50 was determined again 30 minutes after ablation. To determine the importance of the ablation region, this protocol was repeated in another 5 pigs with ablation at the LV base. Delivered Voltage (401±60 versus 323±50 V) and energy (11±3 versus 7±2 J) for the ULV50 were significantly decreased after LV apex ablation by 19% and 34%, respectively. However, no difference existed in ULV50 before and after LV base ablation. Lesions at both the LV apex and base were subendocardial and ranged from 0.8 to 1.1 cm in diameter. Conclusions —Subendocardial ablation at the apical LV markedly decreases ULV50, which suggests that the activation originating from this postshock early site is responsible for VF initiation and that interventions to electrically silence this site can influence the outcome of VF induction by ULV shocks.