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- Bikdeli, Behnood, et al.
(author)
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Individual Patient Data Pooled Analysis of Randomized Trials of Bivalirudin versus Heparin in Acute Myocardial Infarction : Rationale and Methodology
- 2020
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In: Thrombosis and Haemostasis. - : Georg Thieme Verlag KG. - 0340-6245 .- 2567-689X. ; 120:2, s. 348-361
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Journal article (peer-reviewed)abstract
- Background Individual randomized controlled trials (RCTs) of periprocedural anticoagulation with bivalirudin versus heparin during percutaneous coronary intervention (PCI) have reported conflicting results. Study-level meta-analyses lack granularity to adjust for confounders, explore heterogeneity, or identify subgroups that may particularly benefit or be harmed.Objective To overcome these limitations, we sought to develop an individual patient-data pooled database of RCTs comparing bivalirudin versus heparin.Methods We conducted a systematic review to identify RCTs in which ≥1,000 patients with acute myocardial infarction (AMI) undergoing PCI were randomized to bivalirudin versus heparin.Results From 738 identified studies, 8 RCTs met the prespecified criteria. The principal investigators of each study agreed to provide patient-level data. The data were pooled and checked for accuracy against trial publications, with discrepancies addressed by consulting with the trialists. Consensus-based definitions were created to resolve differing antithrombotic, procedural, and outcome definitions. The project required 3.5 years to complete, and the final database includes 27,409 patients (13,346 randomized to bivalirudin and 14,063 randomized to heparin).Conclusion We have created a large individual patient database of bivalirudin versus heparin RCTs in patients with AMI undergoing PCI. This endeavor may help identify the optimal periprocedural anticoagulation regimen for patient groups with different relative risks of adverse ischemic versus bleeding events, including those with ST-segment and non-ST-segment elevation MI, radial versus femoral access, use of a prolonged bivalirudin infusion or glycoprotein inhibitors, and others. Adherence to standardized techniques and rigorous validation processes should increase confidence in the accuracy and robustness of the results..
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| 2. |
- Zou, Zhengping, et al.
(author)
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Dominant flow structure in the squealer tip gap and its impact on turbine aerodynamic performance
- 2017
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In: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 138, s. 167-184
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Journal article (peer-reviewed)abstract
- Tip leakage loss reduction is important for improving the turbine aerodynamic performance. In this paper, the flow field of a transonic high pressure turbine stage with a squealer tip is numerically investigated. The physical mechanism of flow structures inside the cavity that control leakage loss is presented, which is obtained by analyzing the evolution of the flow structures and its influence on the leakage flow rate and momentum at the gap outlet. The impacts of the aerodynamic conditions and geometric parameters, such as blade loading distributions in the tip region, squealer heights, and gap heights, on leakage loss reduction are also discussed. The results show that the scraping vortex generated inside the cavity is the dominant flow structure affecting turbine aerodynamic performance. An aero-labyrinth liked sealing effect is formed by the scraping vortex, which increases the energy dissipation of the leakage flow inside the gap and reduces the equivalent flow area at the gap outlet. The discharge coefficient of the squealer tip is therefore decreased, and the tip leakage loss is reduced accordingly. Variations in the blade loading distribution in the tip region and the squealer geometry change the scraping vortex characteristics, such as the size, intensity, and its position inside the cavity, resulting in a different controlling effect on leakage loss. By reasonable blade tip loading distribution and squealer tip geometry for organizing scraping vortex characteristics, the squealer tip can improve the turbine aerodynamic performance effectively.
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