Extended Formulations via Decision Diagrams

We propose a general algorithm of constructing an extended formulation for any given set of linear constraints with integer coefficients. Our algorithm consists of two phases: first construct a decision diagram $(V,E)$ that somehow represents a given $m \times n$ constraint matrix, and then build an equivalent set of $|E|$ linear constraints over $n+|V|$ variables. That is, the size of the resultant extended formulation depends not explicitly on the number $m$ of the original constraints, but on its decision diagram representation. Therefore, we may significantly reduce the computation time for optimization problems with integer constraint matrices by solving them under the extended formulations, especially when we obtain concise decision diagram representations for the matrices. We can apply our method to $1$-norm regularized hard margin optimization over the binary instance space $\{0,1\}^n$, which can be formulated as a linear programming problem with $m$ constraints with $\{-1,0,1\}$-valued coefficients over $n$ variables, where $m$ is the size of the given sample. Furthermore, introducing slack variables over the edges of the decision diagram, we establish a variant formulation of soft margin optimization. We demonstrate the effectiveness of our extended formulations for integer programming and the $1$-norm regularized soft margin optimization tasks over synthetic and real datasets

Patency with antiplatelet treatment after vascular access intervention therapy: a retrospective observational study

Abstract Background Vascular access (VA) intervention therapy (VAIVT) has been increasingly used for treating VA failure (VAF) in patients undergoing hemodialysis; however, clinical evidence demonstrating the efficacy of prevention of VAF after VAIVT is limited. Therefore, we aimed to assess characteristics of patients developing VAF after VAIVT and analyze risk factors for VAF after VAIVT. Methods This retrospective study included 96 patients with VAF who underwent ultrasound-guided VAIVT by interventional nephrologists between January 2013 and March 2018 at the Department of Nephrology, University of Tokyo Hospital, Japan. Patient information included age, sex, medication history, and comorbidities that could potentially affect VAF onset. Patients were categorized into two groups based on antiplatelet treatment. Multivariate Cox regression analysis was performed for evaluating effect of various factors on VAF after VAIVT. Results Median age of patients at the time of VAIVT was 71 years (interquartile range 63–79); the most prevalent etiology underlying end-stage renal disease was diabetic nephropathy (40.7%). Comparison between the antiplatelet and non-antiplatelet groups revealed that the incidence of VAF was significantly lower in the antiplatelet group. Multivariate analysis revealed that antiplatelet treatment was associated with a lower risk of VAF after VAIVT. Conclusion Administration of antiplatelet agents was associated with a significant reduction in VAF risk after VAIVT

National trends in the outcomes of subarachnoid haemorrhage and the prognostic influence of stroke centre capability in Japan: retrospective cohort study

Objectives To examine the national, 6-year trends in in-hospital clinical outcomes of patients with subarachnoid haemorrhage (SAH) who underwent clipping or coiling and the prognostic influence of temporal trends in the Comprehensive Stroke Center (CSC) capabilities on patient outcomes in Japan.Design Retrospective study.Setting Six hundred and thirty-one primary care institutions in Japan.Participants Forty-five thousand and eleven patients with SAH who were urgently hospitalised, identified using the J-ASPECT Diagnosis Procedure Combination database.Primary and secondary outcome measures Annual number of patients with SAH who remained untreated, or who received clipping or coiling, in-hospital mortality and poor functional outcomes (modified Rankin Scale: 3–6) at discharge. Each CSC was assessed using a validated scoring system (CSC score: 1–25 points).Results In the overall cohort, in-hospital mortality decreased (year for trend, OR (95% CI): 0.97 (0.96 to 0.99)), while the proportion of poor functional outcomes remained unchanged (1.00 (0.98 to 1.02)). The proportion of patients who underwent clipping gradually decreased from 46.6% to 38.5%, while that of those who received coiling and those left untreated gradually increased from 16.9% to 22.6% and 35.4% to 38%, respectively. In-hospital mortality of coiled (0.94 (0.89 to 0.98)) and untreated (0.93 (0.90 to 0.96)) patients decreased, whereas that of clipped patients remained stable. CSC score improvement was associated with increased use of coiling (per 1-point increase, 1.14 (1.08 to 1.20)) but not with short-term patient outcomes regardless of treatment modality.Conclusions The 6-year trends indicated lower in-hospital mortality for patients with SAH (attributable to better outcomes), increased use of coiling and multidisciplinary care for untreated patients. Further increasing CSC capabilities may improve overall outcomes, mainly by increasing the use of coiling. Additional studies are necessary to determine the effect of confounders such as aneurysm complexity on outcomes of clipped patients in the modern endovascular era