1,720,966 research outputs found
Asymptomatic aortic dissection associated with a mitral prosthetic leak: a clinical case report
No full textA case of aortic dissection ("DeBakey type III") in an asymptomatic 78-year-old woman is described. The patient underwent a mitral valve replacement (bioprosthesis Sorin) in June 1990 for severe mitral stenosis; in October 1990 she was admitted to our hospital for severe dyspnea and cardiac failure with good response to medical treatment. The routine echo color Doppler examination showed only a hint of paraprosthetic leak, which required further investigation by transesophageal echocardiography. This approach revealed the presence of a regurgitant jet extending from the prosthetic mitral valve toward the atrial septum. The examination of the thoracic aorta revealed the presence of a dissection flap; the color Doppler technique showed a bidirectional flow through the site of communication between the two lumina. The extension of the dissection from the aortic arch to the origin of the renal branches was confirmed by computerized axial tomography. We emphasize the importance of the transesophageal approach in elderly patients with aortic dissection, often asymptomati
Hemodynamic response to somatostatin at rest and during sympathetic activation in idiopathic orthostatic hypotension
No full textIdiopathic orthostatic hypotension (IOH) represents a degenerative disorder of the peripheral nervous system characterized by low values of arterial blood pressure during orthostatism, with reduction in serum catecholamines. Since treatment of symptomatic IOH has been unsatisfactory till now, we studied the hemodynamic response to somatostatin (S) (Octreotide, 100 micrograms sc) at rest (R) and during sympathetic activation (tilting, T) by means of 2D and/or color Doppler echocardiography, in 5 ambulatory IOH patients (4M, 1F; aged 65 +/- 5 years), with simultaneous recording of blood pressure and heart rate. Post-S, an increased blood pressure was evident during T without heart rate modifications (pre- vs post-S, SAP: 92 +/- 9 vs 148 +/- 12; DAP: 61 +/- 4 vs 90 +/- 9 mmHg; p less than 0.05), while systolic echo parameters did not change significantly. Doppler aortic velocity curve showed during T a reduction of Vmax (pre- vs post-S: 0.98 +/- 0.09 vs 0.73 +/- 0.03 m/s; p less than 0.05) and of cardiac output, due to unchanged preload. Pre-S, at rest, Doppler mitral velocity curve presented a normal E/A ratio as in normal subjects, with a reduced E peak and an increased A peak post-S, indirect signs of increased afterload. Pre-S, E and A peak velocities underwent progressive decrease during T, markedly more evident post-S. Total peripheral resistance, at rest and during T, increased post-S too (pre- vs post-S, rest: 2406 +/- 267 vs 3162 +/- 599; T: 1634 +/- 201 vs 2784 +/- 425 dyne*s/cm-5; p less than 0.05
The role of mitral regurgitation in the neurovegetative regulation of mitral valve prolapse
No full textTo define the role of mitral regurgitation (MR) on sympatho-vagal balance in mitral valve prolapse (MVP) patients, we analyzed 41 ambulatory MVP symptomatic patients. Twenty-seven patients (4 males, 23 females, aged 34 +/- 3 years) had significative MR assessed color Doppler, while 14 patients (5 males, 9 females, aged 29 +/- 3 years) had no MR; 36 age- and sex-matched subjects were studied as controls (C). Spectral analysis of heart rate variability (HRV) was performed at rest and during sympathetic activation (tilt). In the whole group of MVP patients spectral components did not differ significantly from C at rest and during tilt. When patients were subdivided in relation to the presence (+) or absence (-) of MR, HRV revealed in MR+ patients at rest an increased high frequency (HF) and a diminished low frequency (LF) component (47 +/- 5 and 41 +/- 5 normalized units, nu) with respect to C (34 +/- 3 and 54 +/- 3 nu, p < 0.05, respectively). Viceversa during tilt, in MR+ patients it was possible to observe a LF increase greater than in C (delta LF: 36 +/- 4 versus 25 +/- 3 nu, p < 0.05). As HF component is currently interpreted as a marker of vagal modulation of HRV, our results suggest an increased vagal tone associated with MR possibly due to stimulation of atrial vagal receptors; moreover, an increased sympathetic responsiveness to tilt seems to characterize MR+ patients
Multiplanar transesophageal echocardiography in a case of hypernephroma
No full textA 78-year-old man admitted to our hospital with signs and symptoms of right ventricular failure, consisting of severe edema of the scrotum and the penis, ankle edema, hepatomegaly, and a history of asthenia associated with a recent weight loss. Two-dimensional echocardiography showed an intracavitary mass in the right atrium and a moderate pericardial effusion; the remaining structures were normal. To better define the origin of this mass, transesophageal echocardiography was performed. The mass extended from the inferior vena cava with no sites of attachment to the atrial wall. The mass was elongated, mobile, with a triangular termination near the tricuspid valve, without signs of right ventricular obstruction. An abdominal-pelvic CT scan demonstrated the origin of the mass at the superior pole of the left kidney extending through the renal vein and the inferior vena cava into the right atrium. The mass was surgically removed and the pathological examination revealed a renal cell carcinoma (hypernephroma) of the clear cells subtype. After surgery, the patient did well with the resolution of the picture of right ventricular failur
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
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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