1,721,222 research outputs found
Assessment of subendocardial structure and function
No full textThe combination of high energy expenditure and the borderline adequacy of perfusion make the subendocardium uniquely vulnerable to injury. Selective subendocardial involvement is usually a marker of subclinical disease. Technical advances in new noninvasive imaging modalities, especially in spatial resolution, now permit qualitative and quantitative assessment of subendocardial structure, function, and perfusion. Many newer techniques have the potential to provide superior prognostic information to current standard assessment methods. This review describes the contemporary capabilities of multiple imaging modalities for assessment of the subendocardium, and seeks to guide the clinician regarding the information and technical deficiencies of each modality. © 2010 American College of Cardiology Foundation.No Full Tex
Hemodynamic benefit of rest and exercise optimization of cardiac resynchronization therapy
No full textThe optimal method of cardiac resynchronization therapy (CRT) optimization is as yet unknown. We sought to investigate the responses of optimization at rest and on exercise. This 2 stage study involved 59 patients (age 65 ± 10, 75% male), who had all recently undergone successful CRT implantation. In the first stage, the 6-month response was compared between 30 individuals who underwent resting echocardiographic optimization of CRT [atrioventricular (AV delay) plus ventriculo-ventricular delays (VV delay)], compared with the 29 who did not. In the second stage, a subset of 37 patients from the original cohort were randomized (double-blind) to either resting echocardiographic optimization (n = 20) or exercise echocardiographic optimization (n = 17) and followed for a further 6 months. Clinical and echocardiographic data were collected at each stage. Patients undergoing rest optimization demonstrated improvement in almost all variables and significantly in B-type natriuretic peptide (BNP) in contrast to those without optimization. In a linear regression model, the only significant predictor of BNP change was whether an individual underwent resting optimization or not (β = 0.38, P = 0.04). In those undergoing resting optimization, the degree of change in AV delay was correlated with improvement in left ventricle (LV) end-diastolic volume (r2 = 0.33, P < 0.01). Optimization on exercise was associated with a significant decrease in 6-minute walk test compared to those randomized to rest optimization possibly due to inducing nonoptimization at rest. In conclusion, echocardiographic optimization of CRT at rest is superior to no optimization or optimization on exercise. Patients with the greatest change in AV delay to reach optimal may undergo greater LV remodeling.No Full Tex
Prediction of all-cause mortality from global longitudinal speckle strain: Comparison with ejection fraction and wall motion scoring
No full textBackground-Although global left ventricular systolic function is an important determinant of mortality, standard measures such as ejection fraction (EF) and wall motion score index (WMSI) have important technical limitations. The aim of this study was to compare global longitudinal speckle strain (GLS), an automated technique for measurement of long-axis function, with EF and WMSI for the prediction of mortality.Methods and Results-Of 546 consecutive individuals undergoing echocardiography for assessment of resting left ventricular function, 91 died over a period of 5.2±1.5 years. In addition to Simpson biplane EF, WMSI was determined by 2 experienced readers and GLS was calculated from 3 standard apical views using 2D speckle tracking. The incremental value of EF, WMSI, and GLS to significant clinical variables was assessed in nested Cox models. Clinical factors associated with outcome (model x22=20.2) were age (hazard ratio [HR], 1.46; P35% and those with and without wall motion abnormalities. A GLS ≥-12% was found to be equivalent to an EF ≤35% for the prediction of prognosis. Intraobserver and interobserver variations for EF and GLS were similar. Conclusions-GLS is a superior predictor of outcome to either EF or WMSI and may become the optimal method for assessment of global left ventricular systolic function. (Circ Cardiovasc Imaging. 2009;2:356-364.) Copyright © 2009 American Heart Association, Inc.No Full Tex
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
Association of Myocardial Deformation With Mortality Independent of Myocardial Ischemia and Left Ventricular Hypertrophy
No full textObjectives: The aim of this study was to investigate the relative contributions of left ventricular hypertrophy (LVH) and myocardial ischemia to the association between abnormal myocardial deformation during dobutamine stress echocardiography (DSE) and mortality. Background: Both left ventricular hypertrophy (LVH) and myocardial ischemia are known to convey a significant adverse prognostic impact. In addition, myocardial deformation is an independent predictor of outcome in patients undergoing DSE. The mechanism of this association, however, is undefined. Methods: We studied 223 consecutive individuals with normal resting LV function undergoing DSE. The LV mass was indexed to height (g/m2.7) (LVMI), and LVH was designated as LVMI ≥51 g/m2.7. Myocardial ischemia was defined on the basis of new, inducible wall motion abnormalities. Customized software was used to measure global strain rate (SRs), which was averaged in 18 myocardial segments at peak stress. Individuals were followed for all-cause mortality over a mean of 5.4 ± 1.4 years. Results: Left ventricular hypertrophy was identified in 83 individuals (37%), and 63 (28%) had ischemia documented at DSE. In a Cox proportional hazards model, the strongest predictor of all-cause mortality for the total population was SRs (hazard ratio: 2.16, 95% confidence interval: 1.63 to 2.87, p < 0.01). Both LVH (p < 0.01) and ischemia (p < 0.05) had a significant adverse prognostic impact. Individuals with both LVH and ischemia had the worst outcome (p = 0.02) in comparison with the rest of the population. Among LV geometric patterns, concentric LVH had the worst outcome (p < 0.01). However, SRs was the strongest predictor of mortality in both LVH and ischemia. In a model reflecting clinical practice, SRs provided a significant increment in model power over baseline and variables identified at DSE. Conclusions: The SRs is a powerful, independent predictor of all-cause mortality in individuals undergoing DSE and provides incremental information over baseline clinical and echocardiographic variables. Whereas SRs is influenced by both LVH and myocardial ischemia, both independently and additively, its predictive power for mortality is independent of both.No Full Tex
Secondary prevention in coronary artery disease: a risk-guidance may be beneficial
No full textBackground
Assessment of secondary event risk is now recommended for all coronary artery disease (CAD) patients. Many risk calculators have been developed for this purpose. However, their contribution to secondary prevention of CAD is limited because it is unknown whether high-risk patients would benefit more from intensive management. This study sought to apply a previously developed risk score of secondary event to predict readmission in CAD patients, and determine if higher-risk patients benefit more from intensive medical and interventional therapies.
Methods
This State-wide longitudinal study included 19,940 patients admitted to a hospital in 2010 with CAD as the principal diagnosis. Patients were followed up till the end of 2015. A previously developed and validated risk score (PEGASUS-TIMI54) was used to estimate risks of future adverse events and stratify all patients into either low risk (score<6) or high risk (score≥6) as previously recommended. The primary outcome was all-cause readmission. Secondary outcomes included all-cause mortality and days alive and out of hospital within five years of hospital discharge. Cox proportional hazards regression and linear regression were used for analysis.
Results
The high risk patients (n=6,573) had a significantly higher proportion of males and Indigenous people, had greater comorbidities, and were more likely to be readmitted or dead (all p<0.001) than their counterparts in the low risk group (n=13,367). Beta-blocker (hazards ratio HR=0.87 [95% CI: 0.79–0.95]), ACEi/ARB (HR=0.68 [95% CI: 0.62–0.73]) and PCI (HR=0.91 [95% CI: 0.88–0.95]) were negatively associated with readmission, and showed a negative interaction (p<0.001) with patients' predicted risks – implicating greater benefits for high-risk patients. CABG, on the contrary, was positively associated with readmission (HR=1.44 [95% CI: 1.15–1.80]) and showed a negative interaction (p<0.001) with patients' predicted risks. This finding suggests that patients receiving CABG were more likely to be readmitted than those not receiving CABG, but this trend reduced for patients with higher risks. Analysis of secondary outcomes suggest that all medical and interventional therapies reduced mortality risks, with the strongest effect size for CABG (HR=0.34 [95% CI: 0.29–0.48]). There was a negative interaction of statins, PCI and CABG with patients' predicted risks, implicating greater survival benefits for patients with higher risks.
Conclusions
CAD patients can be effectively risk-stratified. The use of this information for a risk-guided strategy may maximize benefits for high-risk patients.No Full Tex
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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