1,721,071 research outputs found
Disproportionate secondary mitral regurgitation: Myths, misconceptions and clinical implications
No full textSecondary (functional) mitral regurgitation (SMR) most commonly arises secondary to left ventricular (LV) dilation/dysfunction. The concept of disproportionately severe SMR was proposed to help explain the different results of two randomised trials of transcatheter edge-to-edge mitral valve repair (TEER) versus medical therapy. This concept is based on the fact that effective regurgitant orifice area (EROA) depends on LV end-diastolic volume (LVEDV), ejection fraction, regurgitant fraction and the velocity-time integral of SMR. This review focuses on the haemodynamic framework underlying the concept and the myths and misconceptions arising from it. Each component of EROA/LVEDV is prone to measurement error which can result in misclassification of individual patients. Moreover, EROA is typically measured at peak systole rather than its mean value over the duration of MR. This can result in physiologically impossible values of EROA or regurgitant volume. Although the EROA/LVEDV ratio (1) emphasises that grading MR severity needs to consider LV size and function and (2) helps explain the different outcomes between COAPT and MITRAFR, there are important factors that are not included. Among these are left atrial compliance, LV pressure and ejection fraction, pulmonary hypertension, right ventricular function and tricuspid regurgitation. Because medical therapy can reduce LV volumes and improve both LV function and SMR severity, the key to patient selection is forced titration of neurohormonal antagonists to the target doses that have been proven in clinical trials (along with cardiac resynchronisation when appropriate). Patients who continue to have symptomatic severe SMR after doing so should be considered for TEER
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Bivalirudin versus heparin with or without glycoprotein IIb/IIIa inhibitors in patients with STEMI undergoing primary PCI: An updated meta-analysis of 10,350 patients from five randomized clinical trials
No full textAIMS: To evaluate the impact of bivalirudin versus heparin on efficacy and safety outcomes of ST-segment elevation myocardial infarction (STEMI) patients undergoing primary percutaneous coronary intervention (PCI) and to explore the impact of differential use (bailout vs. routine) of glycoprotein IIb/IIIa inhibitors (GPI).METHODS AND RESULTS: Five randomized controlled trials encompassing 10,350 patients were included. Primary efficacy and safety endpoints were all-cause death and major bleeding, respectively. All-cause death at 30 days did not significantly differ with bivalirudin compared to heparin (odds ratio (OR) 0.97, 95% confidence interval (CI) 0.74-1.28; P=0.84). Major bleeding was significantly reduced by bivalirudin compared to heparin (OR 0.58, 95% CI 0.40-0.85; P=0.005). Bivalirudin use was associated with non-significantly different rates of 30-day definite stent thrombosis (ST) (OR 1.71, 95% CI 0.84-3.49; P=0.14), albeit with higher rates of acute ST (OR 3.55, 95% CI 1.67-7.56; P=0.001) and non-significantly different rates of subacute ST (OR 0.86, 95% CI 0.46-1.61; P=0.64). There were non-significant differences in the 30-day rates of reinfarction (OR 1.47, 95% CI 0.94-2.30; P=0.10) and cardiovascular death (OR 0.76, 95% CI 0.56-1.02; P=0.07). There were no significant interactions between bailout versus routine GPI use in the heparin arm for any of the safety or efficacy outcomes (all Pinteraction>0.10).CONCLUSIONS: Bivalirudin compared with heparin was associated with comparable 30-day rates of mortality with reduced major bleeding, at the price of an increased risk of acute ST, with non-significant differences in the overall 30-day rates of ST and reinfarction. Intended use of GPI in the heparin arm did not significantly modify the treatment effects of bivalirudin. Given the important differences between trials, as well as evolution in technique and adjunct pharmacotherapy, further randomized trials are warranted to discriminate whether there are substantial safety and efficacy differences between these agents during primary PCI in STEMI
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