1,721,030 research outputs found
Ludwig Rehn (1849-1930): the German surgeon who performed the worldwide first successful cardiac operation.
No full textLudwig Rehn, a German surgeon, performed the worldwide first successful cardiac operation in 1896 when he repaired a stab wound to the heart by direct suture. When he presented his work one year later at a surgical conference this pioneering operation evoked considerable ethical discussion. Rehn's surgical contributions also include carrying out the first thyroidectomy in 1880 and clarifying the causes of cancer in workers in the local aniline factories
MDCT in the diagnostic algorithm in patients with symptomatic atrial fibrillation.
No full textAtrial fibrillation (AF) is the most common supraventricular arrhythmia and a major cause of morbidity. Arrhythmogenic foci originating within the pulmonary veins (PVs) are an important cause of both paroxysmal and persistent AF. A variety of endovascular and surgical techniques have been used to electrically isolate the PV from the left atrium. Pulmonary venography for localization of the PV ostium can be difficult to perform during the ablation procedure. While the anatomy of the PV is patient-specific, non-invasive imaging techniques may provide useful diagnostic information prior to the intended intervention. In this context, multidetector computed tomography (MDCT) visualization of the left atrial and PV anatomy prior to left atrial ablation and PV isolation is becoming increasingly important. MDCT imaging provides pre-procedural information on the left atrial anatomy, including atrial size and venous attachments, and it may identify potential post-procedural complications, such as pulmonary vein stenosis or cardiac perforations. Here, we review the relevant literature and present the current "state-of-the-art" of left atrial anatomy, PV ostia as well as the clinical aspects of refractory AF, MDCT imaging protocols and procedural aspects of PV ablation
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
Direct pro-arrhythmogenic effects of angiotensin II can be suppressed by AT1receptor blockade in human atrial myocardium
No full textAtrial fibrillation (AF) is the most common cardiac arrhythmia in clinical practice. Indirect evidence from clinical trials demonstrates that chronic inhibition of the renin-angiotensin-system (RAS) significantly reduces the incidence of AF. Since mechanisms of this protective effect of RAS-blockade are poorly understood, we directly tested proarrhythmic effects of angiotensin II (Ang II) in human atrial myocardium. Methods: Isolated trabeculae from human atrial appendages (n = 80) were electrically stimulated. We assessed isometric force and incidence of arrhythmic extra contractions (AECs) with and without increasing concentrations of Ang II (1-1000 nmol/L) in the absence or presence of receptor-blockade by saralasin (non-specific ATR-antagonist), irbesartan (AT1R-antagonist) or PD123319 (AT2R-antagonist). Results: Twitch force and AECs concentration-dependently increased with Ang II. Effects became significant at concentrations > 1 nmol/L Ang II and were maximal at 1000 nmol/L (increase in twitch force to 157 +/- 14% and AECs from 0 to 80%) saralasin and irbesartan partially prevented the inotropic effect of 100 nmol/L Ang II (by 45 +/- 12% and 68 +/- 6%; p < 0.05), and completely prevented the occurrence of AECs. Conclusion: Ang II exerts direct pro-arrhythmic effects in human atrial myocardium. These effects are mediated by AT I-receptors and can be prevented by AT1R-blockade. This mechanism may contribute to the beneficial effects of RAS-blockade on AF in clinical trials. (C) 2008 Published by Elsevier B.V. on behalf of European Society of Cardiology
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
Inhibition of CaMKII Attenuates Progressing Disruption of Ca2+ Homeostasis Upon Left Ventricular Assist Device Implantation in Human Heart Failure
No full textIn heart failure, left ventricular assist device (LVAD) implantation is performed to ensure sufficient cardiac output. Whereas some patients are subsequently weaned from LVAD support, other patients still need heart transplantation. To elucidate underlying mechanisms, we assessed the arrhythmogenic SR-Ca2+ leak at the time of LVAD implantation (HF-Im) and heart transplantation (HF-Tx) and evaluated the effects of CaMKII-inhibition. Human left-ventricular cardiomyocytes were isolated, paced at 1Hz for 10 beats to ensure SR-Ca2+ loading and scanned for diastolic Ca2+ sparks (confocal microscopy). In HF-Im, the high diastolic spark frequency (CaSpF) of 0.76 +/- 0.12x100m(-1)xs(-1) could be reduced to 0.48 +/- 0.10x100m(-1)xs(-1) by CaMKII inhibition (AIP, 1M). The amplitude of Ca2+ sparks, width, and length was not significantly altered. In sum, CaMKII inhibition yielded a clear tendency toward a reduction of the SR-Ca2+ leak (n cells/patients=76/6 vs. 108/6, P=0.08). In HF-Tx, we detected an even higher CaSpF of 1.00 +/- 0.10 100m(-1)xs(-1) and a higher SR-Ca2+ leak compared with HF-Im (increase by 81 +/- 33%, n cells/patients=156/7 vs. 130/7, P<0.05), which fits to the further decreased LV function. Here, CaMKII inhibition likewise reduced CaSpF (0.35 +/- 0.09 100m(-1)xs(-1,)P=0.06) and significantly reduced spark duration (n sparks/patients=58/3 vs. 159/3, P<0.05). Conclusively, the SR-Ca2+ leak was reduced by 69 +/- 12% in HF-Tx upon CaMKII inhibition (n cells/patients=53/3 vs. 91/3, P<0.05). These data show that the SR-Ca2+ leak correlates with the development of LV function after LVAD implantation and may represent an important pathomechanism. The fact that CaMKII inhibition reduces the SR-Ca2+ leak in HF-Tx suggests that CaMKII inhibition may be a promising option to beneficially influence clinical course after LVAD implantation
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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