1,720,961 research outputs found
Clinical use of body surface potential mapping in cardiac arrhythmias
No full textThe electrocardiology and specifically body surface potential maps (BSPM) have two main objectives in the arrhythmologic field: 1) identification of signs of susceptibility to arrhythmias, and 2) identification of site of origin of the arrhythmias. In order to detect the susceptibility to ventricular arrhythmias, maps were recorded with different lead systems by different authors and, in particular, various methods of analysis of BSPM have been used to study repolarization potentials: QRST integral maps, eigenvector analysis, principal component analysis, autocorrelation analysis. From these analyses several markers of vulnerability to arrhythmias were identified, which demonstrated a predictive accuracy of various degree in selected patient populations. As concerns the identification of site of origin of the arrhythmias, the use of 62 leads BSPMs during endocardial pace mapping technique enabled more precise identification of the site of origin of postinfarction ventricular tachycardia episodes, compared with the use of the 12-lead electrocardiography (ECG). Recently a new electrocardiographic modality (ECG-imaging) enabled to compute non-invasively and with high resolution epicardial potential distribution and epicardial activation sequences from potentials recorded on the body surface together with cardiac computed tomography images. The ECG-imaging has been successfully applied in humans using geometrical information from computed tomography of each subject, in different heart conditions: normal heart, heart with a conduction disorder, focal activation initiated by right or left ventricular pacing, focal ventricular tachycardia and atrial flutter
The effect of intrathoracic heart position on electrocardiogram autocorrelation maps
No full textWe studied the influence of the heart position in the thorax on the autocorrelation (AC) maps consisting of correlation coefficients between each pair of instantaneous electrocardiogram potential distributions over a time interval. We used a thorax-shaped electrolytic-filled tank with an isolated and perfused dog heart placed at positions spanning 5 cm on each space direction. The correlation coefficient between QRST AC maps was in the range of 0.92 to 0.99, whereas the correlation coefficient between the corresponding QRST integral maps was in the range of 0.55 to 0.87, proving that AC maps are less influenced by the heart position than integral maps. Thus, diagnostic indexes computed from the AC maps can be expected to be more specific to phenomena taking place in the myocardium than to criteria based directly on electrocardiogram amplitudes in various leads. (copyright) 2005 Elsevier Inc. All rights reserved
Early ventricular repolarization (J wave): association with other repolarization features
No full textOrthogonal components of the body surface repolarization map and the depolarization pattern.
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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
Prognostic value for ventricular tachicardia of indices of ventricular repolarization in patients with and without myocardial infarction
No full textVariations 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
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