Lattice Boltzmann method for warm fluid simulations of plasma wakefield acceleration

A comprehensive characterization of lattice Boltzmann (LB) schemes to perform warm fluid numerical simulations of particle wakefield acceleration (PWFA) processes is discussed in this paper. The LB schemes we develop hinge on the moment matching procedure, allowing the fluid description of a warm relativistic plasma wake generated by a driver pulse propagating in a neutral plasma. We focus on fluid models equations resulting from two popular closure assumptions of the relativistic kinetic equations, i.e., the local equilibrium and the warm plasma closure assumptions. The developed LB schemes can thus be used to disclose insights on the quantitative differences between the two closure approaches in the dynamics of PWFA processes. Comparisons between the proposed schemes and available analytical results are extensively addressed.Comment: 8 figure

Papillary muscle intervention vs mitral ring annuloplasty in ischemic mitral regurgitation

Background and Aims The main pathophysiological factor of chronic ischemic mitral regurgitation (MR) is the outward displacement of the papillary muscles (PMs) leading to leaflet tethering. For this reason, papillary muscle intervention (PMI) in combination with mitral ring annuloplasty (MRA) has recently been introduced into clinical practice to correct this displacement, and to reduce the recurrence of regurgitation. Methods A meta‐analysis was conducted comparing the outcomes of PMI and MRA performed in combination vs MRA performed alone, in terms of MR recurrence and left ventricular reverse remodeling (LVRR). A meta‐regression was carried out to investigate the impact of the type of PMI procedure on the outcomes. Results MR recurrence in patients undergoing both PMI and MRA was lower than in those who only had MRA (log incidence rate ratio, −0.66; lower‐upper limits, −1.13 to 0.20; I2 = 0.0%; p = .44; Egger's test: intercept 0.35 [−0.78 to 1.51]; p = .42). The group with both PMI and MRA and that with only MRA showed a slightly higher reduction in left ventricular diameters (−5.94%; −8.75% to 3.13%,). However, in both groups, LVRR was p = .33). Conclusions Using PMI and MRA together has a lower MR recurrence than using MRA alone. No significant LVRR was observed between the two groups nor between the PMI techniques employed

Surgical Risk Factors for Ischemic Stroke Following Coronary Artery Bypass Grafting. A Multi-Factor Multimodel Analysis

Background: Ischemic stroke after coronary artery bypass (CABG) has been often linked to aortic manipulation during surgery. Objectives: The objective of the study was to estimate the rate of postoperative ischemic stroke within 30 days from CABG by surgical risk factors alone or in combination. Methods: The multinomial propensity score for multiple treatments was used to create six models with a total of 16,255 consecutive patients undergoing isolated CABG. For each model, a different classification variable was used to stratify patients. Results: Balance achieved in all models was substantial, enabling unbiased estimation of the treatment estimand. Both off-pump techniques with (0.009; 95% CI 0.006–0.011) or without proximal anastomoses (0.005; 0.005–0.003), and surgery performed on the beating heart using cardiopulmonary bypass with (0.009; 0.006–0.011) or without proximal anastomoses (0.024; 0.021–0.029) showed a mean stroke estimate significantly lower than the other techniques. Off-pump surgery and on-pump surgery without an aortic cross-clamp yielded nearly equal incidences of stroke (0.012; 0.008–0.015 and 0.018; 0.012–0.023, respectively). Using an aortic cross-clamp significantly increased the stroke estimate (0.075; 0.061–0.088), whereas using a side-biting clamp did not (0.039; 0.033–0.044). The number of aortic touches (0.029; 0.026–0.031) and the number of proximal anastomoses (0.044; 0.035–0.047) did not significantly increase the incidence of stroke. Conclusions: Aortic cross-clamping was found to be the primary cause of post-CABG ischemic stroke. Instead, additional aortic manipulation from a side-biting clamp, on-pump surgery, multiple aortic touches, number of proximal anastomoses, and aortic cannulation were found not to increase the estimate of stroke significantly. Further research on this topic is warranted

The use of both internal thoracic arteries for coronary revascularization increases the estimate of post-operative lower limb ischemia in patients with peripheral artery disease

Background Patients with a history of peripheral arterial disease (PAD) undergoing coronary artery bypass grafting (CABG) exhibit higher rates of complications. There are conflicting data on the survival benefits for bilateral thoracic artery (BITA) grafting compared with left internal thoracic artery (LITA) CABG in patients with PAD. The aim of the study was to explore the influence of the use of BITA grafts vs. LITA for CABG on post-operative acute lower limb ischemia (ALLI) and main post-operative complications in patients with concomitant PAD. Methods We used a propensity-score (PS) based analysis to compare outcomes between the two surgical procedures, BITA and LITA. The inverse probability of treatment weighting PS technique was applied to adjust for pre- and intra-operative confounders, and to get optimal balancing of the pre-operative data. The primary outcome was the estimate of postoperative ALLI. Secondary outcomes included overall death and death of cardiac causes within 30 days of surgery, stroke and acute kidney disease (AKD). Results The study population consisted of 1961 patients. The LITA procedure was performed in 1768 patients whereas 193 patients underwent a BITA technique. The estimate of ALLI was 14% higher in the BITA compared to the LITA (p <0.001) group. Thirty-day mortality, cardiac death, occurrence of stroke and AKI did not differ significantly between the groups. Conclusions The use of both ITAs led to a significant increase in ALLI. This result was most likely caused by the complete disruption of the ITA collateral providing additional blood supply to the lower extremities. Based on our data, BITA should be used with extreme caution in PAD patients. Further research on this topic is necessary to confirm our findings

Patient survival in severe low-flow, low-gradient aortic stenosis after aortic valve replacement or conservative management

Background and aim Classical and paradoxical low-flow, low-gradient (LFLG) aortic stenosis (AS) are the most challenging subtypes of AS. The current therapeutic options are aortic valve replacement (AVR) and conservative management: AVR promotes long-term survival but is invasive, while conservative management yields a poor prognosis but is noninvasive since it uses no aortic valve replacement (noAVR). The present meta-analysis investigated the rate of survival of patients with LFLG AS undergoing either AVR or noAVR interventions.Methods The meta-analysis compared the outcomes of AVR with those of noAVR in terms of patient survival. In both groups, a meta-regression was conducted to investigate the impact on patient survival of the left ventricular ejection fraction (LVEF), either preserved (paradoxical LFLG AS) or reduced (classical LFLG AS).Results The relative risk of survival between the AVR and noAVR groups was 1.99 [1.40, 2.82] (p = .0001), suggesting that survival tends to be better in AVR patients than in noAVR patients. The meta-regression revealed that a reduced LVEF may be related to a higher survival in AVR patients when compared to a preserved LVEF (p = .04). Finally, the analysis indicated that LVEF seems not to be prognostic of survival in noAVR patients (p = .18).Conclusions Patients with LFLG AS have better survival if they undergo AVR. In AVR patients, reduced LVEF rather than preserved LVEF is related to better survival, whereas there seems to be no difference in prognostic value between reduced and preserved LVEF in noAVR patients.</p

Lattice Boltzmann simulations of Plasma Wakefield Acceleration

We explore a novel simulation route for Plasma Wakefield Acceleration (PWFA) by using the computational method known as the Lattice Boltzmann Method (LBM). LBM is based on a discretization of the continuum kinetic theory while assuring the convergence towards hydrodynamics for coarse-grained fields (i.e., density, velocity, etc.). LBM is an established numerical analysis tool in computational fluid dynamics, able to efficiently bridge between kinetic theory and hydrodynamics, but its application in the context of PWFA has never been investigated so far. This paper aims at filling this gap. Results of LBM simulations for PWFA are discussed and compared with those of a code (Architect) implementing a Cold Fluid (CF) model for the plasma. In the hydrodynamic framework, we discuss the importance of regularization effects related to diffusion properties intrinsic of the LBM, allowing to go beyond the traditional CF approximations. Issues on computational efficiency are also addressed

Machine Learning to Identify Patients at Risk of Developing New-Onset Atrial Fibrillation after Coronary Artery Bypass

Background: This study aims to get an effective machine learning (ML) prediction model of new-onset postoperative atrial fibrillation (POAF) following coronary artery bypass grafting (CABG) and to highlight the most relevant clinical factors. Methods: Four ML algorithms were employed to analyze 394 patients undergoing CABG, and their performances were compared: Multivariate Adaptive Regression Spline, Neural Network, Random Forest, and Support Vector Machine. Each algorithm was applied to the training data set to choose the most important features and to build a predictive model. The better performance for each model was obtained by a hyperparameters search, and the Receiver Operating Characteristic Area Under the Curve metric was selected to choose the best model. The best instances of each model were fed with the test data set, and some metrics were generated to assess the performance of the models on the unseen data set. A traditional logistic regression was also performed to be compared with the machine learning models. Results: Random Forest model showed the best performance, and the top five predictive features included age, preoperative creatinine values, time of aortic cross-clamping, body surface area, and Logistic Euro-Score. Conclusions: The use of ML for clinical predictions requires an accurate evaluation of the models and their hyperparameters. Random Forest outperformed all other models in the clinical prediction of POAF following CABG

The Impact of Preoperative Inflammatory Markers on the Prognosis of Patients Undergoing Surgical Resection of Pulmonary Oligometastases

The aim of this study was to assess the prognostic value of preoperative neutrophil-to-lymphocyte ratio (NLR) and C-reactive protein (CRP) levels in patients undergoing resection of pulmonary oligometastases. A retrospective analysis on 141 patients undergoing a first pulmonary metastasectomy in a single center was carried out. Two distinct analysis were performed subdividing patients according to their NLR ratio and CRP level. The main outcomes were survival and time to recurrence. At completion of follow-up 74 patients were still alive (52.5%). Subdividing patients according to their NLR yielded a significant difference in five-year progression-free survival (PFS, NLR = 4:18%, p = 0.01). When subdivided by their CRP levels, patients with preoperative CRP <5 mg/L demonstrated higher values of five-year overall survival (OS, 57% vs. 34%, p = 0.006) and five-year PFS (35% vs. 22%, p = 0.04). At multivariate analysis, level of neutrophils (p = 0.009) and lung comorbidities (p = 0.021) were independent predictors of death, whereas preoperative CRP (p = 0.002), multiple metastases (p = 0.003) and presence of lung comorbidities (p = 0.001) were independent predictors of recurrence. NLR and CRP are important predictors of prognostic outcome in patients undergoing pulmonary metastasectomy