1,721,006 research outputs found
The Prognostic Value of Electrocardiographic Alternans in the Primary Prevention on Patients Having an Implantable Cardioverter Defibrillator
No full textPrimary prevention therapy with implantable cardioverter defibrillator (ICD) may benefit in specificity evaluating the left ventricular ejection fraction together with other electrocardiogram (ECG)-derived cardiac risk indexes, such as ECG alternans (ECGA). ECGA, the ABAB morphology fluctuation of ECG waves (P wave/QRS complex/T wave), results in P-wave/QRS/T-wave alternans (PWA/QRSA/TWA). This work aims to validate ECGA prognostic value on ECGs acquired from ICD patients (Leiden University Medical Center Database). Thus, 82 controls (ICD therapy was not needed) and 40 cases (ICD therapy was needed) were enrolled. ECGA was analyzed by the enhanced adaptive matched filter method at rest and exercise. Median ECGA features (amplitude-Am, duration-D, area-Ar, magnitude-M) were computed over leads and ICD groups. ECGA ability to discriminate between ICD groups was evaluated by the area under the curve (AUC) of the receiver operating characteristic curve. Precordial leads allowed a better discrimination than all leads (higher AUC). QRSA, at both rest (controls/cases: Am=5/10 μV, D=33/45 beats, Ar=360/760 μV·ms, M=351/603 μV·beats) and exercise (controls/cases: Am=16/20 μV, D=55/57 beats, Ar=1280/1600 μV·ms, M=992/1316 μV·beats) has the best discriminant power, with AUC values higher than 0.7 at rest. ECGA feature normalization by the ECG mean amplitude was also considered. We can conclude that (1) ECGA predictive power is best expressed at rest, and QRSA seems to be the best ECGA form to identify patients who should benefit from primary prevention ICD therapy, (2) normalization seems not to improve our results
Logistic Regression to Enhance Risk Assessment by Left Ventricular Ejection Fraction and f99
No full textSudden cardiac death remains one of the leading causes of death in developed countries. Left ventricular ejection fraction (LVEF) and f99 are two noninvasive indexes of cardiovascular risk (traditional the former and innovative the latter) which, taken singularly, have not shown sufficiently high SCD predictive power to justify preventive actions. Thus, the aim of the present study was to investigate if their combination improves predictability of ventricular arrhythmias. To this aim, ECG recordings from 266 ICD patients, of which 76 developed ventricular tachycardia or fibrillation during the 4-year follow-up (ICD_Cases), and 190 did not (ICD_Controls). The ECGs of each patient was used to compute the f99, a repolarization index defined as the frequency at which the cumulative power energy reaches 99%. Eventually, a logistic regression between LVEF and f99 was performed in order to derive a combined predictor (CP) of ventricular arrhythmia. Goodness of each index was evaluated in terms of the area under the receiver operator curve (AUC). When used singularly, LVEF and f99 respectively provided an AUC of 0.67 and 0.64. When combined to get CP=-0.15-0.05·LVEF+0.03·f99, this provided an AUC of 0.71. In conclusion, use of logistic regression improves LVEF and f99 predictability of ventricular arrhythmias
Heart Rate-Dependent Hysteresis of T-Wave Alternans in Primary Prevention ICD Patients
No full textBackground: T-wave alternans (TWA) is usually performed at accelerated heart rates (HR) during exercise, while recovery TWA is typically not analyzed. Consequently, it is still unknown if TWA shows a HR-dependent hysteresis or not. Thus, the aim of the present study was to investigate TWA dependency on HR during both the exercise and recovery phases of an ergometer test, and to evaluate if recovery TWA may contribute to identify subjects at increased risk of arrhythmic events. Methods: Our HR adaptive match filter was used to identify TWA from electrocardiographic recordings acquired during a bicycle ergometer test in 266 patients with implanted cardio-defibrillator. During the 4-year follow-up, 76 patients developed tachycardia or ventricular fibrillation (ICD_Cases) and 190 did not (ICD_Controls). Results: TWA was statistically lower during exercise than recovery for HRs between 75 and 110 bpm (16-21 μV vs 20-27 μV; P < 0.05), and reverse for HRs between 120 and 130 bpm (41-51 μV vs 28 μV; P < 0.05). ICD_Cases and ICD_Controls showed significantly different TWA at 80 bpm (20 μV vs 15 μV; P < 0.05) and 140 bpm (15 μV vs 22 μV; P < 0.05) during exercise, and at 90 bpm (38 μV vs 21 μV; P < 0.05) and 95 bpm (33-24 μV vs 28 μV; P < 0.05) during recovery. Conclusions: TWA shows a HR-dependent hysteresis and there is a different behavior of TWA in ICD_Cases and ICD_Controls groups. Consequently, beside exercise TWA also recovery TWA may contribute to identify subjects at increased risk of arrhythmic events
MOESM1 of Serial electrocardiography to detect newly emerging or aggravating cardiac pathology: a deep-learning approach
Get PDFAdditional file 1. NeuronWeightAndBias.mat is a Matlab file, that contains the Weights and Biases of the neural network obtained bythe repeated structuring and learning procedure
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
- …
