1,720,985 research outputs found
Cinefluoroscopic identification of Björk-Shiley prosthetic heart valves
No full textNumerous mechanical prostheses are currently utilized for heart valve replacement. Fluoroscopy is a useful technique to identify prosthetic valves, to evaluate their function and to follow-up the patients' condition. Scattered and contrasting data, however, have been reported about the radiographic appearance of Björk-Shiley heart valves. This study shows that each Björk-Shiley valve model has characteristic radiographic features that can be readily determined by fluoroscopic evaluation, leading to easy and accurate non-invasive identification
Valve design characteristics and cine-fluoroscopic appearance of five currently available bileaflet prosthetic heart valves
No full textBileaflet prostheses are low profile, central flow orifice devices that show excellent hemodynamic performance and low thrombogenicity. Five models are currently used for heart valve replacement. Comprehensive and comparative studies regarding valve characteristics and functioning are lacking, making the updating and the familiarization by physicians and cardiologists with these prostheses difficult. We describe the valve design characteristics and evaluate the cine-fluoroscopic appearance and functioning of 387 bileaflet prostheses that have been implanted in 367 consecutive patients. The valve types are St Jude Medical (n = 69), Edwards-Duromedics (n = 74), Carbomedics (n = 1290) Sorin Bicarbon (n = 88) and Jyros (n = 27). The prostheses' fluoroscopic appearance was evaluated through multiple radiographic views (Siemens-Elema equipment with C-arm); the prostheses' functional evaluation was performed by obtaining the "tilting disk projection" (ie, with the radiographic beam parallel to both the valve ring plane and the tilting axis of disks) to calculate opening, closing, and travel angles of the disks. This study shows that each of the five bileaflet valves has distinctive design characteristics. Fluoroscopy is an easy, readily available, and useful technique that correctly identifies the prosthesis type and properly evaluates its functioning in the majority of cases
Straddling endoventricular pericardial patch in mitral valve repair with the sliding leaflet technique
No full textCalcification of the mitral annulus is always a technical complication in mitral surgery and standard procedures are often difficult to perform; mitral valve replacement can be dangerous; with a high risk of perioperative heart rupture, and reconstructive surgery is often contraindicated. Nevertheless in this case of posterior leaflet prolapse with annular calcification valve repair was performed, after complete calcium debridement causing annulus disruption and atrio-ventricular discontinuity, by means of a straddling atrio-ventricular pericardial patch and the sliding leaflet technique
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
Fluoroscopic functional evaluation of bileaflet prostheses: effect of different intraoperative valve orientation
No full textFluoroscopy is a reliable, easy, and readily available technique to follow-up prosthesis functioning after heart valve surgery. The different orientation given to the prosthesis may represent a limitation of the technique accounting for unsatisfactory results in 10% to 40% of the cases. The aim of the study was to evaluate whether and to what extent different intraoperative valve orientation influence feasibility and accuracy of postoperative fluoroscopic evaluation of bileaflet prostheses. We prospectively evaluated 90 patients who had aortic, mitral, and/or tricuspid valve replacement with Sorin Bicarbon or CarboMedics bileaflet prostheses. Fifty percent of the patients in each group were randomly assigned to receive prostheses oriented in a perpendicular or a parallel position with respect to the ventricular septum. Fluoroscopic evaluation was considered appropriate when the prosthesis' "tilting disk" projection was obtained. The valve's hemodynamic performance was investigated through Doppler study. A proper fluoroscopic evaluation was rapidly (15 +/- 5 seconds) achieved in all patients with the former orientation, whereas it was impossible to obtain it in 8 of 20 (40%), 19 of 20 (95%), and 4 of 5 (80%) of patients with the latter orientation. In the remaining patients extremely angulated, uneasy projection was often required to get a correct fluoroscopic image. The Doppler study showed a similarly favorable hemodynamic performance regardless of valve orientation. Prosthesis orientation crucially affects the rate of success of the fluoroscopic evaluation. The orientation perpendicular to the ventricular septum greatly facilitates the postoperative feasibility and accuracy of fluoroscopy, and it is not detrimental to the valve's hemodynamic performance. This valve orientation may provide a better fluoroscopic window whenever a valve dysfunction is suspected
EVOLUTION DE L'INSUFFISANCE TRICUSPIDALE SECONDAIRE A LA MALADIE MITRALE APRES TRAITEMENT CHIRURGICAL DE SUBSTITUTION DE LA VALVE MITRALE
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