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Sleep-disordered breathing (SDB) is associated with an increased risk of adverse events in patients with heart failure (HF); however, its impact in patients implanted with a left ventricular assist device (LVAD) remains unclear. We aimed to investigate the prevalence of SDB in patients with LVAD and its impact on their clinical outcomes. Fifty consecutive patients with LVAD who underwent portable sleep monitoring between September 2017 and April 2018 were prospectively enrolled, and they were followed up for 170 ± 36 days. According to their respiratory disturbance indexes (RDIs), they were categorized into the SDB group (RDI ≥ 15, n = 12) and the non-SDB group (RDI 15, n = 38). The incidence of adverse events during the follow-up period was investigated after enrollment. Multivariate logistic regression analysis revealed significant differences in SDB in LVAD-implanted patients in terms of the logarithmic transformation brain natriuretic peptide (BNP) values (p = 0.005). The optimal BNP cut-off value for SDB prediction in LVAD-implanted patients was 300 pg/mL (sensitivity: 58.3%, specificity: 94.7%). During follow-up, ventricular tachyarrhythmias (VTas) occurred significantly more frequently in the SDB group (4 [33%] vs. 2 [5%] patients, p = 0.02); Atrial tachyarrhythmia (ATa) also tended to occur more frequently in the SDB group (2 [25%] vs. 2 [2%] patients, p = 0.07). SBD was prevalent in 24% of the LVAD-implanted patients with advanced HF. Furthermore, SDB was significantly associated with high BNP levels and was also potentially associated with subsequent incidence of VTa in patients with LVAD.

We present computational flow analysis of a vertical-axis wind turbine (VAWT) that has been proposed to also serve as a tsunami shelter. In addition to the three-blade rotor, the turbine has four support columns at the periphery. The columns support the turbine rotor and the shelter. Computational challenges encountered in flow analysis of wind turbines in general include accurate representation of the turbine geometry, multiscale unsteady flow, and moving-boundary flow associated with the rotor motion. The tsunami-shelter VAWT, because of its rather high geometric complexity, poses the additional challenge of reaching high accuracy in turbine-geometry representation and flow solution when the geometry is so complex. We address the challenges with a space–time (ST) computational method that integrates three special ST methods around the core, ST Variational Multiscale (ST-VMS) method, and mesh generation and improvement methods. The three special methods are the ST Slip Interface (ST-SI) method, ST Isogeometric Analysis (ST-IGA), and the ST/NURBS Mesh Update Method (STNMUM). The ST-discretization feature of the integrated method provides higher-order accuracy compared to standard discretization methods. The VMS feature addresses the computational challenges associated with the multiscale nature of the unsteady flow. The moving-mesh feature of the ST framework enables high-resolution computation near the blades. The ST-SI enables moving-mesh computation of the spinning rotor. The mesh covering the rotor spins with it, and the SI between the spinning mesh and the rest of the mesh accurately connects the two sides of the solution. The ST-IGA enables more accurate representation of the blade and other turbine geometries and increased accuracy in the flow solution. The STNMUM enables exact representation of the mesh rotation. A general-purpose NURBS mesh generation method makes it easier to deal with the complex turbine geometry. The quality of the mesh generated with this method is improved with a mesh relaxation method based on fiber-reinforced hyperelasticity and optimized zero-stress state. We present computations for the 2D and 3D cases. The computations show the effectiveness of our ST and mesh generation and relaxation methods in flow analysis of the tsunami-shelter VAWT.

Gastrointestinal bleeding (GIB) is among the major complications affecting implantable continuous-flow left ventricular assist device (iLVAD) recipients and is the major cause of re-hospitalization. GIB in iLVAD recipients is sometimes critical, and controlling bleeding using conventional approaches is difficult. A 35-year-old woman developed refractory GIB from multiple gastric polyps and de novo angiodysplasia after Jarvik2000® iLVAD implantation. Discontinuation of anticoagulation and antiplatelet therapies had little effect on GIB; thus, multiple endoscopic hemostatic therapies were performed. However, bleeding recurred several times, and red blood cell (RBC) transfusion in large volumes was required for progressive anemia. Furthermore, the von Willebrand factor (VWF) multimer analysis revealed loss of the high-molecular weight multimer, which may have resulted from the high-speed rotation of the axial-flow LVAD pump. To supplement VWF, cryoprecipitate was administered, but it was effective for only several days. Finally, the patient was treated with octreotide, a somatostatin analog, on post-operative day 58. After starting octreotide, tarry stool gradually decreased, and progression of anemia slowed down within the first 14 days of treatment; thus, the total RBC transfusion volume was reduced without additional hemostatic interventions, including cryoprecipitate administration. The patient developed mediastinitis on post-operative day 68 and died of sepsis on post-operative day 72. There was no adverse effect associated with octreotide use. Although the observation period was short, octreotide appears to be useful for resolving recurrent GIB after iLVAD implantation and reducing blood transfusions.