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Hiroo Takayama - One of the best experts on this subject based on the ideXlab platform.
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left ventricular decompression during speed optimization ramps in patients supported by continuous flow left ventricular assist devices device specific performance characteristics and impact on diagnostic algorithms
Journal of Cardiac Failure, 2015Co-Authors: Nir Uriel, A R Garan, M Yuzefpolskaya, A P Levin, G Sayer, Kanika P Mody, Sunu S Thomas, Sirtaz Adatya, Alexander Breskin, Hiroo TakayamaAbstract:Abstract Background Echocardiographic ramp tests have been widely used to help guide speed adjustments and for identification of potential device Malfunctions in patients with axial continuous-flow left ventricular assist devices (LVADs) (Heartmate II LVAD [HMII]). Recently, the use of centrifugal-flow LVADs (Heartware LVAD [HVAD]) has been on the rise. The purpose of this study was to evaluate the utility of ramp tests for assessing ventricular decompression in HVAD patients. Methods and Results In this prospective study, ramp tests were performed before index hospitalization discharge or at the time of device Malfunction. Vital signs, device parameters (including flow), and echocardiographic parameters (including left ventricular end-diastolic dimension [LVEDD], frequency of aortic valve [AV] opening, and valvular insufficiency) were recorded in increments of 100 rpm, from 2,300 rpm to 3,200 rpm. Twenty-six ramp tests were performed, 19 for speed optimization and 7 for device Malfunction assessment. The average speed after the speed optimization ramp tests was 2,534.74 ± 156.32 RPM, and the AV closed at a mean speed of 2,751.77 ± 227.16 rpm, with 1 patient's valve remaining open at the maximum speed. The reduction in LVEDD for each speed increase was significantly different when the AV was open or closed, at −0.09 cm/increment and −0.15 cm/increment, respectively ( P = .013), which is significantly different than previously established HMII LVEDD slopes. There were also significant changes in overall device flow ( P = .001), upper flow ( P = .031), and lower flow ( P = .003) after AV closure. The power slope did not change significantly after the AV closed ( P = .656). Five of the 19 tests were stopped before completion owing to suction events, but all tests reached ≥3,000 rpm. Conclusions The parameter slopes for the HMII cannot be directly applied to ramp studies in HVAD patients. Overall, the LVEDD slope is drastically smaller in magnitude than the previously reported HMII findings, and speed adjustments were not based on the degree of left ventricular unloading. Therefore, the slope of the LVEDD-rpm relationship is not likely to be helpful in evaluating HVAD function.
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development of a novel echocardiography ramp test for speed optimization and diagnosis of device thrombosis in continuous flow left ventricular assist devices the columbia ramp study
Journal of the American College of Cardiology, 2012Co-Authors: Nir Uriel, Kerry A Morrison, A R Garan, Tomoko S Kato, M Yuzefpolskaya, F Latif, S Restaino, Donna Mancini, M Flannery, Hiroo TakayamaAbstract:Objectives This study sought to develop a novel approach to optimizing continuous-flow left ventricular assist device (CF-LVAD) function and diagnosing device Malfunctions. Background In CF-LVAD patients, the dynamic interaction of device speed, left and right ventricular decompression, and valve function can be assessed during an echocardiography-monitored speed ramp test. Methods We devised a unique ramp test protocol to be routinely used at the time of discharge for speed optimization and/or if device Malfunction was suspected. The patient's left ventricular end-diastolic dimension, frequency of aortic valve opening, valvular insufficiency, blood pressure, and CF-LVAD parameters were recorded in increments of 400 rpm from 8,000 rpm to 12,000 rpm. The results of the speed designations were plotted, and linear function slopes for left ventricular end-diastolic dimension, pulsatility index, and power were calculated. Results Fifty-two ramp tests for 39 patients were prospectively collected and analyzed. Twenty-eight ramp tests were performed for speed optimization, and speed was changed in 17 (61%) with a mean absolute value adjustment of 424 ± 211 rpm. Seventeen patients had ramp tests performed for suspected device thrombosis, and 10 tests were suspicious for device thrombosis; these patients were then treated with intensified anticoagulation and/or device exchange/emergent transplantation. Device thrombosis was confirmed in 8 of 10 cases at the time of emergent device exchange or transplantation. All patients with device thrombosis, but none of the remaining patients had a left ventricular end-diastolic dimension slope >−0.16. Conclusions Ramp tests facilitate optimal speed changes and device Malfunction detection and may be used to monitor the effects of therapeutic interventions and need for surgical intervention in CF-LVAD patients.
Nir Uriel - One of the best experts on this subject based on the ideXlab platform.
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left ventricular decompression during speed optimization ramps in patients supported by continuous flow left ventricular assist devices device specific performance characteristics and impact on diagnostic algorithms
Journal of Cardiac Failure, 2015Co-Authors: Nir Uriel, A R Garan, M Yuzefpolskaya, A P Levin, G Sayer, Kanika P Mody, Sunu S Thomas, Sirtaz Adatya, Alexander Breskin, Hiroo TakayamaAbstract:Abstract Background Echocardiographic ramp tests have been widely used to help guide speed adjustments and for identification of potential device Malfunctions in patients with axial continuous-flow left ventricular assist devices (LVADs) (Heartmate II LVAD [HMII]). Recently, the use of centrifugal-flow LVADs (Heartware LVAD [HVAD]) has been on the rise. The purpose of this study was to evaluate the utility of ramp tests for assessing ventricular decompression in HVAD patients. Methods and Results In this prospective study, ramp tests were performed before index hospitalization discharge or at the time of device Malfunction. Vital signs, device parameters (including flow), and echocardiographic parameters (including left ventricular end-diastolic dimension [LVEDD], frequency of aortic valve [AV] opening, and valvular insufficiency) were recorded in increments of 100 rpm, from 2,300 rpm to 3,200 rpm. Twenty-six ramp tests were performed, 19 for speed optimization and 7 for device Malfunction assessment. The average speed after the speed optimization ramp tests was 2,534.74 ± 156.32 RPM, and the AV closed at a mean speed of 2,751.77 ± 227.16 rpm, with 1 patient's valve remaining open at the maximum speed. The reduction in LVEDD for each speed increase was significantly different when the AV was open or closed, at −0.09 cm/increment and −0.15 cm/increment, respectively ( P = .013), which is significantly different than previously established HMII LVEDD slopes. There were also significant changes in overall device flow ( P = .001), upper flow ( P = .031), and lower flow ( P = .003) after AV closure. The power slope did not change significantly after the AV closed ( P = .656). Five of the 19 tests were stopped before completion owing to suction events, but all tests reached ≥3,000 rpm. Conclusions The parameter slopes for the HMII cannot be directly applied to ramp studies in HVAD patients. Overall, the LVEDD slope is drastically smaller in magnitude than the previously reported HMII findings, and speed adjustments were not based on the degree of left ventricular unloading. Therefore, the slope of the LVEDD-rpm relationship is not likely to be helpful in evaluating HVAD function.
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development of a novel echocardiography ramp test for speed optimization and diagnosis of device thrombosis in continuous flow left ventricular assist devices the columbia ramp study
Journal of the American College of Cardiology, 2012Co-Authors: Nir Uriel, Kerry A Morrison, A R Garan, Tomoko S Kato, M Yuzefpolskaya, F Latif, S Restaino, Donna Mancini, M Flannery, Hiroo TakayamaAbstract:Objectives This study sought to develop a novel approach to optimizing continuous-flow left ventricular assist device (CF-LVAD) function and diagnosing device Malfunctions. Background In CF-LVAD patients, the dynamic interaction of device speed, left and right ventricular decompression, and valve function can be assessed during an echocardiography-monitored speed ramp test. Methods We devised a unique ramp test protocol to be routinely used at the time of discharge for speed optimization and/or if device Malfunction was suspected. The patient's left ventricular end-diastolic dimension, frequency of aortic valve opening, valvular insufficiency, blood pressure, and CF-LVAD parameters were recorded in increments of 400 rpm from 8,000 rpm to 12,000 rpm. The results of the speed designations were plotted, and linear function slopes for left ventricular end-diastolic dimension, pulsatility index, and power were calculated. Results Fifty-two ramp tests for 39 patients were prospectively collected and analyzed. Twenty-eight ramp tests were performed for speed optimization, and speed was changed in 17 (61%) with a mean absolute value adjustment of 424 ± 211 rpm. Seventeen patients had ramp tests performed for suspected device thrombosis, and 10 tests were suspicious for device thrombosis; these patients were then treated with intensified anticoagulation and/or device exchange/emergent transplantation. Device thrombosis was confirmed in 8 of 10 cases at the time of emergent device exchange or transplantation. All patients with device thrombosis, but none of the remaining patients had a left ventricular end-diastolic dimension slope >−0.16. Conclusions Ramp tests facilitate optimal speed changes and device Malfunction detection and may be used to monitor the effects of therapeutic interventions and need for surgical intervention in CF-LVAD patients.
Kai Chen - One of the best experts on this subject based on the ideXlab platform.
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error tolerant address configuration for data center networks with Malfunctioning devices
International Conference on Distributed Computing Systems, 2012Co-Authors: Kai Chen, Yan Chen, Che Zhang, Hongtao Zhang, Kai Zheng, Xianda SunAbstract:Address auto-configuration is a key problem in data center networks, where servers and switches encode topology information into their addresses for routing. A recent work DAC [2] has been introduced to address this problem. Without Malfunctions, DAC can auto-configure all the devices quickly. But in case of Malfunctions, DAC requires significant human efforts to correct Malfunctions and it can cause substantial operation delay of the whole data center. In this paper, we further optimize address auto-configuration process even in the presence of Malfunctions. Instead of waiting for all the Malfunctions to be corrected, we could first configure the devices that are not involved in Malfunctions and let them work first. This idea can be translated to considerable practical benefits because in most cases Malfunctions in data centers only account for a very small portion. To realize the idea, we conceptually remove the Malfunctions from the physical data center topology graph and mathematically convert the address configuration problem into induced sub graph isomorphism problem, which is NP-complete. We then introduce an algorithm that can solve the induced sub graph isomorphism quickly by taking advantage of data center topology characteristics and induced sub graph properties. We extensively evaluate our design on representative data center structures with various Malfunction scenarios. The evaluation results demonstrate that the proposed framework and algorithm are efficient and labor-free to deal with the mapping task in the presence of error devices.
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dac generic and automatic address configuration for data center networks
IEEE ACM Transactions on Networking, 2012Co-Authors: Kai Chen, Zhenqian Feng, Chuanxiong Guo, Jing Yuan, Yan ChenAbstract:Data center networks encode locality and topology information into their server and switch addresses for performance and routing purposes. For this reason, the traditional address configuration protocols such as DHCP require a huge amount of manual input, leaving them error-prone. In this paper, we present DAC, a generic and automatic Data center Address Configuration system. With an automatically generated blueprint that defines the connections of servers and switches labeled by logical IDs, e.g., IP addresses, DAC first learns the physical topology labeled by device IDs, e.g., MAC addresses. Then, at the core of DAC is its device-to-logical ID mapping and Malfunction detection. DAC makes an innovation in abstracting the device-to-logical ID mapping to the graph isomorphism problem and solves it with low time complexity by leveraging the attributes of data center network topologies. Its Malfunction detection scheme detects errors such as device and link failures and miswirings, including the most difficult case where miswirings do not cause any node degree change.We have evaluated DAC via simulation, implementation, and experiments. Our simulation results show that DAC can accurately find all the hardest-to-detect Malfunctions and can autoconfigure a large data center with 3.8 million devices in 46 s. In our implementation, we successfully autoconfigure a small 64-server BCube network within 300 ms and show that DAC is a viable solution for data center autoconfiguration.
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Generic and automatic address configuration for data center networks
Computer Communication Review, 2010Co-Authors: Kai Chen, Zhenqian Feng, Chuanxiong Guo, Jing Yuan, Songwu Lu, Haitao Wu, Yan Chen, Wenfei WuAbstract:Data center networks encode locality and topology information into their server and switch addresses for performance and routing purposes. For this reason, the traditional address configuration protocols such as DHCP require huge amount of manual input, leaving them error-prone. In this paper, we present DAC, a generic and automatic Data center Address Configuration system. With an automatically generated blueprint which defines the connections of servers and switches labeled by logical IDs, e.g., IP addresses, DAC first learns the physical topology labeled by device IDs, e.g., MAC addresses. Then at the core of DAC is its device-to-logical ID mapping and Malfunction detection. DAC makes an innovation in abstracting the device-to-logical ID mapping to the graph isomorphism problem, and solves it with low time-complexity by leveraging the attributes of data center network topologies. Its Malfunction detection scheme detects errors such as device and link failures and miswirings, including the most difficult case where miswirings do not cause any node degree change. We have evaluated DAC via simulation, implementation and experiments. Our simulation results show that DAC can accurately find all the hardest-to-detect Malfunctions and can autoconfigure a large data center with 3.8 million devices in 46 seconds. In our implementation, we successfully autoconfigure a small 64-server BCube network within 300 milliseconds and show that DAC is a viable solution for data center autoconfiguration. ? 2010 ACM.
A R Garan - One of the best experts on this subject based on the ideXlab platform.
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left ventricular decompression during speed optimization ramps in patients supported by continuous flow left ventricular assist devices device specific performance characteristics and impact on diagnostic algorithms
Journal of Cardiac Failure, 2015Co-Authors: Nir Uriel, A R Garan, M Yuzefpolskaya, A P Levin, G Sayer, Kanika P Mody, Sunu S Thomas, Sirtaz Adatya, Alexander Breskin, Hiroo TakayamaAbstract:Abstract Background Echocardiographic ramp tests have been widely used to help guide speed adjustments and for identification of potential device Malfunctions in patients with axial continuous-flow left ventricular assist devices (LVADs) (Heartmate II LVAD [HMII]). Recently, the use of centrifugal-flow LVADs (Heartware LVAD [HVAD]) has been on the rise. The purpose of this study was to evaluate the utility of ramp tests for assessing ventricular decompression in HVAD patients. Methods and Results In this prospective study, ramp tests were performed before index hospitalization discharge or at the time of device Malfunction. Vital signs, device parameters (including flow), and echocardiographic parameters (including left ventricular end-diastolic dimension [LVEDD], frequency of aortic valve [AV] opening, and valvular insufficiency) were recorded in increments of 100 rpm, from 2,300 rpm to 3,200 rpm. Twenty-six ramp tests were performed, 19 for speed optimization and 7 for device Malfunction assessment. The average speed after the speed optimization ramp tests was 2,534.74 ± 156.32 RPM, and the AV closed at a mean speed of 2,751.77 ± 227.16 rpm, with 1 patient's valve remaining open at the maximum speed. The reduction in LVEDD for each speed increase was significantly different when the AV was open or closed, at −0.09 cm/increment and −0.15 cm/increment, respectively ( P = .013), which is significantly different than previously established HMII LVEDD slopes. There were also significant changes in overall device flow ( P = .001), upper flow ( P = .031), and lower flow ( P = .003) after AV closure. The power slope did not change significantly after the AV closed ( P = .656). Five of the 19 tests were stopped before completion owing to suction events, but all tests reached ≥3,000 rpm. Conclusions The parameter slopes for the HMII cannot be directly applied to ramp studies in HVAD patients. Overall, the LVEDD slope is drastically smaller in magnitude than the previously reported HMII findings, and speed adjustments were not based on the degree of left ventricular unloading. Therefore, the slope of the LVEDD-rpm relationship is not likely to be helpful in evaluating HVAD function.
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development of a novel echocardiography ramp test for speed optimization and diagnosis of device thrombosis in continuous flow left ventricular assist devices the columbia ramp study
Journal of the American College of Cardiology, 2012Co-Authors: Nir Uriel, Kerry A Morrison, A R Garan, Tomoko S Kato, M Yuzefpolskaya, F Latif, S Restaino, Donna Mancini, M Flannery, Hiroo TakayamaAbstract:Objectives This study sought to develop a novel approach to optimizing continuous-flow left ventricular assist device (CF-LVAD) function and diagnosing device Malfunctions. Background In CF-LVAD patients, the dynamic interaction of device speed, left and right ventricular decompression, and valve function can be assessed during an echocardiography-monitored speed ramp test. Methods We devised a unique ramp test protocol to be routinely used at the time of discharge for speed optimization and/or if device Malfunction was suspected. The patient's left ventricular end-diastolic dimension, frequency of aortic valve opening, valvular insufficiency, blood pressure, and CF-LVAD parameters were recorded in increments of 400 rpm from 8,000 rpm to 12,000 rpm. The results of the speed designations were plotted, and linear function slopes for left ventricular end-diastolic dimension, pulsatility index, and power were calculated. Results Fifty-two ramp tests for 39 patients were prospectively collected and analyzed. Twenty-eight ramp tests were performed for speed optimization, and speed was changed in 17 (61%) with a mean absolute value adjustment of 424 ± 211 rpm. Seventeen patients had ramp tests performed for suspected device thrombosis, and 10 tests were suspicious for device thrombosis; these patients were then treated with intensified anticoagulation and/or device exchange/emergent transplantation. Device thrombosis was confirmed in 8 of 10 cases at the time of emergent device exchange or transplantation. All patients with device thrombosis, but none of the remaining patients had a left ventricular end-diastolic dimension slope >−0.16. Conclusions Ramp tests facilitate optimal speed changes and device Malfunction detection and may be used to monitor the effects of therapeutic interventions and need for surgical intervention in CF-LVAD patients.
M Yuzefpolskaya - One of the best experts on this subject based on the ideXlab platform.
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left ventricular decompression during speed optimization ramps in patients supported by continuous flow left ventricular assist devices device specific performance characteristics and impact on diagnostic algorithms
Journal of Cardiac Failure, 2015Co-Authors: Nir Uriel, A R Garan, M Yuzefpolskaya, A P Levin, G Sayer, Kanika P Mody, Sunu S Thomas, Sirtaz Adatya, Alexander Breskin, Hiroo TakayamaAbstract:Abstract Background Echocardiographic ramp tests have been widely used to help guide speed adjustments and for identification of potential device Malfunctions in patients with axial continuous-flow left ventricular assist devices (LVADs) (Heartmate II LVAD [HMII]). Recently, the use of centrifugal-flow LVADs (Heartware LVAD [HVAD]) has been on the rise. The purpose of this study was to evaluate the utility of ramp tests for assessing ventricular decompression in HVAD patients. Methods and Results In this prospective study, ramp tests were performed before index hospitalization discharge or at the time of device Malfunction. Vital signs, device parameters (including flow), and echocardiographic parameters (including left ventricular end-diastolic dimension [LVEDD], frequency of aortic valve [AV] opening, and valvular insufficiency) were recorded in increments of 100 rpm, from 2,300 rpm to 3,200 rpm. Twenty-six ramp tests were performed, 19 for speed optimization and 7 for device Malfunction assessment. The average speed after the speed optimization ramp tests was 2,534.74 ± 156.32 RPM, and the AV closed at a mean speed of 2,751.77 ± 227.16 rpm, with 1 patient's valve remaining open at the maximum speed. The reduction in LVEDD for each speed increase was significantly different when the AV was open or closed, at −0.09 cm/increment and −0.15 cm/increment, respectively ( P = .013), which is significantly different than previously established HMII LVEDD slopes. There were also significant changes in overall device flow ( P = .001), upper flow ( P = .031), and lower flow ( P = .003) after AV closure. The power slope did not change significantly after the AV closed ( P = .656). Five of the 19 tests were stopped before completion owing to suction events, but all tests reached ≥3,000 rpm. Conclusions The parameter slopes for the HMII cannot be directly applied to ramp studies in HVAD patients. Overall, the LVEDD slope is drastically smaller in magnitude than the previously reported HMII findings, and speed adjustments were not based on the degree of left ventricular unloading. Therefore, the slope of the LVEDD-rpm relationship is not likely to be helpful in evaluating HVAD function.
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development of a novel echocardiography ramp test for speed optimization and diagnosis of device thrombosis in continuous flow left ventricular assist devices the columbia ramp study
Journal of the American College of Cardiology, 2012Co-Authors: Nir Uriel, Kerry A Morrison, A R Garan, Tomoko S Kato, M Yuzefpolskaya, F Latif, S Restaino, Donna Mancini, M Flannery, Hiroo TakayamaAbstract:Objectives This study sought to develop a novel approach to optimizing continuous-flow left ventricular assist device (CF-LVAD) function and diagnosing device Malfunctions. Background In CF-LVAD patients, the dynamic interaction of device speed, left and right ventricular decompression, and valve function can be assessed during an echocardiography-monitored speed ramp test. Methods We devised a unique ramp test protocol to be routinely used at the time of discharge for speed optimization and/or if device Malfunction was suspected. The patient's left ventricular end-diastolic dimension, frequency of aortic valve opening, valvular insufficiency, blood pressure, and CF-LVAD parameters were recorded in increments of 400 rpm from 8,000 rpm to 12,000 rpm. The results of the speed designations were plotted, and linear function slopes for left ventricular end-diastolic dimension, pulsatility index, and power were calculated. Results Fifty-two ramp tests for 39 patients were prospectively collected and analyzed. Twenty-eight ramp tests were performed for speed optimization, and speed was changed in 17 (61%) with a mean absolute value adjustment of 424 ± 211 rpm. Seventeen patients had ramp tests performed for suspected device thrombosis, and 10 tests were suspicious for device thrombosis; these patients were then treated with intensified anticoagulation and/or device exchange/emergent transplantation. Device thrombosis was confirmed in 8 of 10 cases at the time of emergent device exchange or transplantation. All patients with device thrombosis, but none of the remaining patients had a left ventricular end-diastolic dimension slope >−0.16. Conclusions Ramp tests facilitate optimal speed changes and device Malfunction detection and may be used to monitor the effects of therapeutic interventions and need for surgical intervention in CF-LVAD patients.
