1,721,118 research outputs found
Assessing suspected angina: requiem for coronary computed tomography angiography or exercise electrocardiogram?
No full textN/
Contrast Stress-Echocardiography Predicts Cardiac Events in Patients with Suspected Acute Coronary Syndrome but Nondiagnostic Electrocardiogram and Normal 12-Hour Troponin
No full textBACKGROUND: No large study has demonstrated that any stress test can risk-stratify future hard cardiac events (cardiac death or myocardial infarction) in patients with suspected acute coronary syndromes (ACS), nondiagnostic electrocardiographic (ECG) findings, and normal troponin levels. The aim of this study was to test the hypothesis that combined contrast wall motion and myocardial perfusion echocardiographic assessment (cMCE) during stress echocardiography can predict long-term hard cardiac events in patients with suspected ACS, nondiagnostic ECG findings, and normal troponin. METHODS: A total of 545 patients referred for contrast stress echocardiography from the emergency department for suspected ACS but nondiagnostic ECG findings and normal troponin levels at 12 hours were followed up for cardiac events. Patients underwent dipyridamole-atropine echocardiography with adjunctive myocardial perfusion imaging using a commercially available ultrasound contrast medium (SonoVue). RESULTS: During a median follow-up period of 12 months, 25 cardiac events (4.6%) occurred (no deaths, 12 nonfatal myocardial infarctions, 13 episodes of unstable angina). Abnormal findings on cMCE were the most significant predictor of both hard cardiac events (hazard ratio, 22.8; 95% confidence interval, 2.9-176.7) and the combined (cardiac death, myocardial infarction, or unstable angina requiring revascularization) end point (hazard ratio, 10.7; 95% confidence interval,3.7-31.3). The inclusion of the cMCE variable significantly improved multivariate models, determining lower Akaike information criterion values and higher discrimination ability. CONCLUSIONS: cMCE during contrast stress echocardiography provided independent information for predicting hard and combined cardiac events beyond that predicted by stress wall motion abnormalities in patients with suspected ACS, nondiagnostic ECG findings, and normal troponin levels.-
Simultaneous Assessment of Myocardial Perfusion, Wall Motion, and Deformation during Myocardial Contrast Echocardiography: A Feasibility Study
No full textThe role of cardiovascular ultrasound for the assessment of coronary artery disease in women
No full textBackground
Cardiovascular disease (CVD) remains the main cause of morbidity and mortality in women.
Guidelines advocate Exercise ECG in intermediate risk women who are able to exercise to diagnose obstructive coronary artery disease (CAD), which is controversial. Due to the low prevalence of obstructive CAD in women, functional testing has a relatively low predictive value for this. Carotid ultrasound can be used to identify carotid plaque and increased carotid intimal-media thickness which are markers of atherosclerosis. Carotid disease has been shown to predict obstructive CAD on coronary angiography.
Methods and Results
I randomised 416 women with suspected CAD, to undergo either exercise electrocardiography (Ex-ECG) or Exercise stress echocardiography (ESE). The positive predictive value (PPV) for both tests was similar, and during follow up there was no difference in cardiac events. Ex-ECG was marginally more cost-effective than ESE. For the second part of this thesis, I prospectively performed carotid ultrasonography on 415 women attending for stress echocardiography. In women with inducible ischaemia and carotid plaque versus no carotid plaque, the prevalence of significant CAD was 71% and 13% respectively (p< 0.001). A high proportion of women classified as low cardiovascular risk were found to have carotid plaque, potentially benefiting from aggressive primary prevention.
Conclusion
In intermediate-risk women, I have shown that a diagnostic strategy that used Ex-ECG had similar efficacy to an ESE strategy. Ex-ECG may be considered a useful initial diagnostic strategy in the absence of ESE, in symptomatic women with suspected CAD. Carotid ultrasound is a useful adjunct to women undergoing stress echocardiography (SE), acting as a superior gatekeeper to invasive coronary angiography over SE alone. It also identifies high risk women, where conventional cardiovascular risk scores underestimate risk.Open Acces
The determinants of intra-plaque neovascularisation: a study by contrast-enhanced carotid ultrasonography
Full text linkAtherosclerosis is a chronic inflammatory disorder, initiated by arterial wall injury, mediated by well-recognised cardiovascular risk factors and culminating in formation of plaques, the patho-biological substrate that precedes events such as stroke and myocardial infarction.
Intraplaque neovascularisation (IPN) is one of several defence mechanisms in response to atherosclerosis. With development of an atherosclerotic plaque within the intima, the distance between the deeper intimal layers and the luminal surface increases, producing hypoxia within the arterial wall. This stimulates release of pro-angiogenic factors that induces neoangiogenesis in an attempt to normalise oxygen tension. However, these neo-vessels are fragile, immature and leaky and thought to be the primary cause of intraplaque haemorrhage, now appreciated to be a key risk factor for plaque rupture. Therefore, the presence of IPN is now widely recognised as a precursor of the “vulnerable plaque”.
Contrast-enhanced ultrasound (CEUS) is a non-invasive method of imaging carotid plaques and, as contrast bubbles travel wherever erythrocytes travel, they permit visualization of IPN. Prior research studies have demonstrated that CEUS can detect IPN with a high degree of accuracy (on comparison with histological plaque specimens) and have shown a relationship between extent of plaque neovessels and plaque echogenicity and between plaque neovascularization and prior cardiovascular events. However, CEUS is a relatively recently described imaging technique and there were a number of unanswered questions in this field, some of which formed the basis for study in this research Thesis. In this Thesis, research studies were conducted on human subjects using CEUS imaging to identify IPN and its determinants.
The incidence and determinants of IPN in healthy asymptomatic individuals was unknown and was studied in subjects from the London Life Sciences Population (LOLIPOP) study, a large study exploring mechanisms for differences in cardiovascular disease (CVD) between South Asian and European White individuals. The study found that approximately half of all plaques contain IPN. The only variable associated with IPN presence in an adjusted analysis was Asian ethnicity. This finding potentially has significant implications as it may help explain, in part, the greater CVD burden observed in Asian populations. A study comparing visualization of the carotid tree during B-mode and CEUS imaging was also conducted. Both IMT visualization and plaque detection were significantly improved by CEUS, implying that CEUS is superior to B-mode imaging for detection of sub-clinical atherosclerosis.
Radiotherapy (RT) damages arterial walls and promotes atherosclerosis. The carotid arteries frequently receive significant incidental doses of radiation during RT treatment of head and neck cancers. The effect of RT on plaque composition – specifically IPN – had not been studied and thus a collaborative cardio-oncological study was conducted to assess the effects of RT upon IPN in cancer survivors who had previously received RT. A significant association between RT and IPN was found which may provide insights into the mechanisms underlying the increased stroke risk amongst cancer survivors treated by RT.
Finally, a collaboration with biophysicists was formed to develop and validate a novel algorithm for quantitative analysis of IPN. Patients clinically scheduled to undergo carotid endarterectomy were recruited and underwent CEUS imaging prior to surgery. This study did not achieve its principal aims due to challenges with patient recruitment, challenges in image quality and with the quantification software also. Future directions of study in this promising field have been addressed in the thesis summary.Open Acces
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
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