Large-scale unit commitment under uncertainty: an updated literature survey

The Unit Commitment problem in energy management aims at finding the optimal production schedule of a set of generation units, while meeting various system-wide constraints. It has always been a large-scale, non-convex, difficult problem, especially in view of the fact that, due to operational requirements, it has to be solved in an unreasonably small time for its size. Recently, growing renewable energy shares have strongly increased the level of uncertainty in the system, making the (ideal) Unit Commitment model a large-scale, non-convex and uncertain (stochastic, robust, chance-constrained) program. We provide a survey of the literature on methods for the Uncertain Unit Commitment problem, in all its variants. We start with a review of the main contributions on solution methods for the deterministic versions of the problem, focussing on those based on mathematical programming techniques that are more relevant for the uncertain versions of the problem. We then present and categorize the approaches to the latter, while providing entry points to the relevant literature on optimization under uncertainty. This is an updated version of the paper "Large-scale Unit Commitment under uncertainty: a literature survey" that appeared in 4OR 13(2), 115--171 (2015); this version has over 170 more citations, most of which appeared in the last three years, proving how fast the literature on uncertain Unit Commitment evolves, and therefore the interest in this subject

Diastolic delta best predicts paravalvular regurgitation after transcatheter aortic valve replacement as assessed by cardiac magnetic resonance: the APPOSE trial

Aims: Paravalvular regurgitation (PVR) is a common complication after transcatheter aortic valve replacement (TAVR) that poses an increased risk of rehospitalization for heart failure and mortality. The aim of this study was to assess the accuracy of haemodynamic indices to predict relevant PVR. Methods and results: In this prospective single-centre clinical trial, four haemodynamic indices of PVR measured during TAVR were assessed for their correlation with gold standard cardiac magnetic resonance (CMR)-derived regurgitant fraction (CMR-RF) at 1 month follow-up: diastolic delta (DD), heart rate-adjusted diastolic delta (HR-DD), aortic regurgitation index (ARI), and aortic regurgitation index ratio (ARI ratio). These haemodynamic indices were analysed for their ability to predict relevant PVR (defined as CMR-RF > 20%) using receiver operating characteristic (ROC) curves with corresponding area under the ROC curves (AUCs). A total of 77 patients were included and had CMR performed 41 ± 14 days after TAVR. Mean CMR-RF was 12.4 ± 9.3%. Fifteen (19.5%) patients had CMR-RF > 20%. DD had the best correlation with CMR-RF and the highest AUC to predict relevant PVR (0.82; 95% CI, 0.72-0.92), followed by HR-DD (AUC 0.78; 95% CI, 0.67-0.89), ARI (AUC 0.78; 95% CI, 0.66-0.89), and ARI ratio (AUC 0.65; 95% CI, 0.49-0.81). The optimal cut-off value for DD was 32 mmHg, with sensitivity of 69% and specificity of 77% in predicting relevant PVR. Conclusion: DD measured during TAVR best predicts relevant PVR. Correction for heart rate (HR-DD) or systolic blood pressure (ARI, ARI ratio) did not improve this predictive value

Transcatheter aortic valve replacement during the COVID-19 pandemic-A Dutch single-center analysis.

Background and Aim of the Study The coronavirus disease 2019 (COVID-19) pandemic has put an enormous strain on healthcare systems and intensive care unit (ICU) capacity, leading to suspension of most elective procedures, including transcatheter aortic valve replacement (TAVR). However, deferment of TAVR is associated with significant wait-time mortality in patients with severe aortic valve stenosis. Conversely, there is currently no data available regarding the safety and feasibility of a continued TAVR program during this unprecedented crisis. The aim of this study is to evaluate the safety and feasibility of patients undergoing TAVR during the COVID-19 pandemic in our center, with specific emphasis on COVID-19 related outcomes. Methods All patients who underwent TAVR in our center between February 27, 2020, and June 30, 2020, were evaluated. Clinical outcomes were described in terms of Valve Academic Research Consortium 2 definitions. Patient follow-up was done by chart review and telephone survey. Results A total of 71 patients have undergone TAVR during the study period. Median age was 80 years, 63% were men, and 25% were inpatients. Procedural success was 99%. After TAVR, 30% involved admission to the ICU, and 94% were ultimately discharged to the cardiac care unit on the same day. Two patients (3%) had confirmed COVID-19 a few days after TAVR, and both died of COVID-19 pneumonia within 2 weeks after hospital discharge. Conclusions A continued TAVR program during the COVID-19 pandemic is feasible despite limited hospital resources. However, COVID-19 related mortality after TAVR is of concern

Construct validity of automated assessment of invasively measured hemodynamics during transcatheter aortic valve replacement

Aims Paravalvular regurgitation (PVR) is frequently observed following Transcatheter Aortic Valve Replacement (TAVR). Periprocedural monitoring of invasive hemodynamics has shown promise for diagnosis of PVR, but automated software options are lacking. We aimed to develop a rule-based algorithm for automated assessment of hemodynamic indices of PVR, and evaluate its construct validity and discriminatory value for cardiac magnetic resonance (CMR)-derived relevant PVR compared to standard manual hemodynamic assessment. Methods and results Left ventricular and aortic pressures were invasively measured during TAVR using fluid-filled pigtail catheters. To evaluate construct validity of automated vs. manual assessment of invasive hemodynamics, we compared (i) proportion of cardiac cycles affected by arrhythmias/noise, (ii) pressure gradients, and (iii) PVR indices. Additionally, we compared the discriminatory value of automatically and manually determined PVR indices for CMR-determined relevant PVR at 30-days. In total, 77 patients were enrolled (664 cardiac cycles). Automated filtering of cardiac cycles affected by arrhythmias/noise had a high sensitivity (95.2%) and specificity (86.4%). In addition, excellent agreement was observed between automated and manual computation of mean gradients pre- and post-TAVR [39.3 ± 12.1 vs. 37.5 ± 11.9 mmHg, intra-class correlation coefficient (ICC): 0.916; 1.92 ± 5.87 vs. 1.14 ± 5.89, ICC: 0.957, respectively], and PVR indices [diastolic delta (DD): 41.7 ± 12.4 vs. 40.6 ± 12.3 mmHg, ICC: 0.982, respectively]. Automated and manual assessment of DD showed comparable discriminatory value for relevant PVR [area under the curve (AUC): 0.81 vs. 0.80, respectively]. Conclusion Rule-based, automated assessment of hemodynamic indices of PVR showed excellent construct validity and discriminatory value for CMR-determined relevant PVR, supporting its use for real-time evaluation and risk stratification in TAVR patients

Left Bundle-Branch Block Induced by Transcatheter Aortic Valve Implantation Increases Risk of Death

Cardiolog