An Observational Overview of Solar Flares

We present an overview of solar flares and associated phenomena, drawing upon a wide range of observational data primarily from the RHESSI era. Following an introductory discussion and overview of the status of observational capabilities, the article is split into topical sections which deal with different areas of flare phenomena (footpoints and ribbons, coronal sources, relationship to coronal mass ejections) and their interconnections. We also discuss flare soft X-ray spectroscopy and the energetics of the process. The emphasis is to describe the observations from multiple points of view, while bearing in mind the models that link them to each other and to theory. The present theoretical and observational understanding of solar flares is far from complete, so we conclude with a brief discussion of models, and a list of missing but important observations.Comment: This is an article for a monograph on the physics of solar flares, inspired by RHESSI observations. The individual articles are to appear in Space Science Reviews (2011

Cost Implications of Left Atrial Appendage Occlusion During Cardiac Surgery: A Cost Analysis of the LAAOS III Trial

: Background The LAAOS III (Left Atrial Appendage Occlusion Study) clinical trial demonstrated that concomitant left atrial appendage (LAA) occlusion leads to a lower risk of ischemic stroke or systemic embolism compared with no occlusion in participants with atrial fibrillation and a CHA2DS2-VASc score of ≥2 undergoing cardiac surgery for another indication. We report the cost implications of concomitant LAA occlusion during cardiac surgery. Methods and Results Using LAAOS III data, we compared the costs (in US dollars) associated with LAA occlusion to no occlusion from the perspective of the Centers for Medicare and Medicaid Services. We calculated the average cost per participant during the trial by applying Medicare reimbursement costs to cardiovascular events for all trial participants. We conducted sensitivity analyses, varying the cost of stroke ±25% and occlusion technique use. Cost neutrality was defined as a mean cost difference within ±5% of the cost per participant in the no-occlusion group. Total study cost per participant was $3878 in the LAA occlusion group and$4490 in the no-occlusion group, a mean difference of -$612 (95$1276 to $45). The main drivers of cost savings were fewer stroke events during the trial (mean difference of -$1021). In sensitivity analyses, LAA occlusion was cost saving for suture and stapler techniques but more expensive with closure device. Conclusions Concomitant LAA occlusion was cost saving for participants in LAAOS III. Our findings support concomitant LAA occlusion as an economically dominant strategy for patients with atrial fibrillation and a CHA2DS2-VASc score of ≥2 undergoing cardiac surgery

Left atrial appendage occlusion during cardiac surgery to prevent stroke

BACKGROUND Surgical occlusion of the left atrial appendage has been hypothesized to prevent ischemic stroke in patients with atrial fibrillation, but this has not been proved. The procedure can be performed during cardiac surgery undertaken for other reasons. METHODS We conducted a multicenter, randomized trial involving participants with atrial fibrillation and a CHA2DS2-VASc score of at least 2 (on a scale from 0 to 9, with higher scores indicating greater risk of stroke) who were scheduled to undergo cardiac surgery for another indication. The participants were randomly assigned to undergo or not undergo occlusion of the left atrial appendage during surgery; all the participants were expected to receive usual care, including oral anticoagulation, during follow-up. The primary outcome was the occurrence of ischemic stroke (including transient ischemic attack with positive neuroimaging) or systemic embolism. The participants, research personnel, and primary care physicians (other than the surgeons) were unaware of the trial-group assignments. RESULTS The primary analysis population included 2379 participants in the occlusion group and 2391 in the no-occlusion group, with a mean age of 71 years and a mean CHA2DS2-VASc score of 4.2. The participants were followed for a mean of 3.8 years. A total of 92.1% of the participants received the assigned procedure, and at 3 years, 76.8% of the participants continued to receive oral anticoagulation. Stroke or systemic embolism occurred in 114 participants (4.8%) in the occlusion group and in 168 (7.0%) in the no-occlusion group (hazard ratio, 0.67; 95% confidence interval, 0.53 to 0.85; P=0.001). The incidence of perioperative bleeding, heart failure, or death did not differ significantly between the trial groups. CONCLUSIONS Among participants with atrial fibrillation who had undergone cardiac surgery, most of whom continued to receive ongoing antithrombotic therapy, the risk of ischemic stroke or systemic embolism was lower with concomitant left atrial appendage occlusion performed during the surgery than without it