Contemporary Management of Ischemic Mitral Regurgitation at Coronary Artery Bypass Grafting

BackgroundRecent guidelines for the treatment of moderate or severe ischemic mitral regurgitation (IMR) in patients undergoing coronary artery bypass grafting (CABG) have changed. This study assessed the real-world impact of changing guidelines on the management of IMR during CABG over time. We hypothesized that the utilization of mitral valve repair for IMR would decrease over time, whereas mitral valve replacement for severe IMR would increase.MethodsPatients undergoing CABG in a statewide collaborative database (2011-2020) were stratified by severity of IMR. Trends in mitral valve repair or replacement were evaluated. To account for differences of the patients, propensity score–matched analyses were used to compare patients with and without mitral intervention.ResultsA total of 11,676 patients met inclusion criteria, including 1355 (11.6%) with moderate IMR and 390 (3.3%) with severe IMR. The proportion of patients undergoing mitral intervention for moderate IMR decreased over time (2011, 17.7%; 2020, 7.5%; P_trend = .001), whereas mitral replacement for severe IMR remained stable (2011, 11.1%; 2020, 13.3%; P_trend = .14). Major morbidity was higher for patients with moderate IMR who underwent mitral intervention (29.1% vs 19.9%; P = .005). In a propensity analysis of 249 well-matched pairs, there was no difference in major morbidity (29.3% with mitral intervention vs 23.7% without; P = .16) or operative mortality (1.2% vs 2.4%; P = .5).ConclusionsConsistent with recent guideline updates, patients with moderate IMR were less likely to undergo mitral repair. However, the rate of replacement for severe IMR did not change. Mitral intervention during CABG did not increase operative mortality or morbidity.     

电子束选区熔化钛合金点阵材料力学性能研究

目的 研究成型工艺和结构设计对电子束选区熔化技术（SEBM）制备的菱形十二面体Ti6Al4V点阵材料相对密度、形貌和压缩性能的影响。方法 点阵的密度通过测定其尺寸和质量得出，采用电子万能试验机测试点阵结构的压缩性能，采用扫描电子显微镜观察点阵表面形貌。结果 SEBM成形Ti6Al4V支架的相对密度随着熔化功率增加和单胞尺寸减小而增大；以等离子旋转电极雾化技术制备的TC4粉末为原料成型的点阵结构具有优异的塑性，压缩应力—应变曲线平台区域波动小；TC4钛合金菱形十二面体多孔材料的密度与屈服强度和弹性模量的关系满足Gibson-Ashby方程，但指数分别为2.34和2.32。结论 通过调控点阵结构设计和SEBM成型工艺，可控制钛合金的孔隙率和压缩性能，满足骨科植入多孔材料需求。     

A High Order Bound Preserving Finite Difference Linear Scheme for Incompressible Flows

We propose a high order finite difference linear scheme combined with a high order bound preserving maximum-principle-preserving (MPP) flux limiter to solve the incompressible flow system. For such problem with highly oscillatory structure but not strong shocks, our approach seems to be less dissipative and much less costly than a WENO type scheme, and has high resolution due to a Hermite reconstruction. Spurious numerical oscillations can be controlled by the weak MPP flux limiter. Numerical tests are performed for the Vlasov-Poisson system, the 2D guiding-center model and the incompressible Euler system. The comparison between the linear and WENO type schemes, with and without the MPP flux limiter, will demonstrate the good performance of our proposed approach.