1,720,960 research outputs found
Sleep-disordered breathing increases the risk of arrhythmias
No full textSleep-disordered breathing (SDB) has been consistently associated with increased risk for cardiovascular diseases, including arrhythmias. The purpose of this review is to elucidate the several pathophysiologic pathways such as repetitive hypoxia and reoxygenation, increased oxidative stress, inflammation and sympathetic activation that may underlie the increased incidence of arrhythmias in SDB patients. We discuss in particular the incidence of ventricular arrhythmias, atrial fibrillation and bradyarrhythmias in SDB patients. In addition, we discuss the electrocardiographic alteration such as ST-T changes during apneic events and QT dispersion induced by SDB that may trigger complex ventricular arrhythmias and sudden cardiac death. Finally, we consider also the therapeutic interventions such as continuous positive airways pressure therapy, a standard treatment for SDB, that may reduce the incidence and recurrence of supraventricular and ventricular arrhythmias in patients with SDB
Role of cardiac electronic implantable device in the stratification and management of embolic risk of silent atrial fibrillation: are all atrial fibrillations created equal?
No full textIntroduction: Ischemic strokes may be associated with atrial fibrillation (AF). AF detection is critical in ischemic stroke survivors, often recommending a switch from antiplatelet therapy to oral anticoagulants for secondary prevention.Areas covered: Cardiac implantable electronic devices (CIED) with their long-term recording capability allows to document AF and to quantify the arrhythmia burden. Recent series in pacemaker and implantable cardioverter-defibrillator (ICD) recipients with no prior stroke showed that short episodes of AF increased stroke risk compared with those without AF recorded. Detection of AF by CIEDs represent a unique opportunity for promp prevention of embolic risk in silent AF. It will be attractive to identify AF before a stroke occurs.Expert commentary: The purpose of this article is to review the role of CIED to detect AF, to quantify the role of AF burden, and to guide primary and secondary stroke prevention
Effect of bosentan on pulmonary hypertension secondary to systolic heart failure
No full textObjectives: The dual endothelin receptor antagonist bosentan improves pulmonary vascular resistance (PVR) in patients with primary pulmonary hypertension (PH). The effects of bosentan on secondary PH due to systolic heart failure (HF) are not well defined. This study evaluates the effect and tolerability of bosentan in patients with PH secondary to HF. Methods: Seventeen adult HF patients with PH and New York Heart Association class III-IV symptoms were treated with bosentan, 62.5 mg twice daily, for 1 month, which was gradually increased to 125 mg twice daily thereafter. Right heart catheterization (RHC), a clinical evaluation and echocardiographic measurements were performed at baseline and at 4 ± 3 (mean ± SD) months of follow-up. Response to bosentan was defined as an improvement in clinical, echocardiographic and RHC parameters. Results: Six patients did not complete the study (therapy was discontinued due to hypotension, elevated liver enzymes or acute decompensation of HF), 11 patients completed the follow-up; 9 patients responded to therapy. Systemic arterial pressures, pulmonary pressures, PVR and the transpulmonary gradient significantly decreased compared with baseline levels in 9 responders (p = 0.05, 0.05, 0.01 and 0.004, respectively), and 4 became eligible for heart transplantation and 3 for left ventricular assist device implantation. Conclusions: Bosentan decreased pulmonary pressures and PVR in the majority of patients with PH secondary to systolic HF, thereby allowing them to be considered candidates for heart transplantation
Left ventricular twisting modifications in patients with left ventricular concentric hypertrophy at increasing after-load conditions
No full textAims: Left ventricular hypertrophy (LVH) develops as a result of several clinical conditions, such as intensive training, hypertension, aortic valve stenosis. Aim of this study was to analyze the left ventricular twist (LVT) modifications in LVH patients with increasing after-load conditions. Methods: A total of 131 patients were enrolled: 17 healthy sedentary people (Hg), without concentric LVH; 45 water polo players (ATg); 22 patients with hypertensive cardiopathy (HPg); 47 patients with different degrees of aortic stenosis (ASg); all patients had concentric LVH, ejection fraction (EF) >54%, and were age-matched. The left ventricular end-systolic wall stress (LV-ESWS) was used as index of after-load. Results: Left ventricular twist value showed a progressive increase from ATg to ASg, according to increasing after-load. Longitudinal left ventricular function by tissue Doppler imaging (TDI) and speckle tracking echocardiography (STE) was reduced in HPg and ASg. There was a negative correlation between LVT and longitudinal systolic function at TDI and STE (r = -0.4; P < 0.001; -0.23; P < 0.05). E/A ratio was lower in HPg and ASg than ATg and Hg. LVT was linearly related to LV-ESWS (r = 0.36; P < 0.01), E/A ratio (r = -0.59; P < 0.001), E/E′ ratio (r = 0.43; P < 0.001), age (r = 0.5; P < 0.001), relative wall thickness (RWT) (r = 0.38; P < 0.01), heart rate (HR) (r = 0.3; P < 0.05), maximum (G. max), and mean transvalvular gradient (G. mean) in ASg (r = 0.37; P < 0.01, r = 0.4; P < 0.01). RWT, E/A ratio, and HR were independent predictor of LVT (β = 0.23; P = 0.007; -0.44; P = 0.001; 0.17; P = 0.049). Only in ASg, G. mean was independent predictor of LVT (β = 0.44; P = 0.01). Conclusion: Left ventricular twist showed a linear trend at increasing after-load values to compensate the reduction in systolic longitudinal function in pathological LVH patients
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
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