1,721,077 research outputs found
The risk of right ventricular failure with current continuous-flow left ventricular assist devices
No full textIntroduction: Right ventricular failure (RVF) still results as the major cause of morbidity and mortality after left ventricular assist device (LVAD) implantation. Despite overall improved outcomes and lower rates of RVF with the use of the newer, continuous-flow (CF) LVADs over pulsatile-flow devices, and development of clinical prediction scores to facilitate preoperative identification of patients at risk for RVF after implantation, RVF occurs in 13% to 40% of continuous-flow device. Areas covered: In this article, a review has been carried out on the current evidence for preoperative assessment of RV function and RVF risk for appropriate patient selection mainly focusing on current imaging and invasive assessment tools. Expert commentary: According to all findings, it is recommended that measurements of RV function should be included in all risk predictions models and that standardization of echocardiographic and hemodynamic evaluation protocols be adopted before and after device implantation across LVAD centers. The balance of well-accepted and fixed multiple variables might be able to better predict the outcomes in such a delicate clinical panorama
Hybrid transcatheter left ventricular reconstruction for the treatment of ischemic cardiomyopathy
Full text linkLeft ventricular (LV) enlargement is a mechanical adaptation to accommodate LV systolic inefficiency following an acute damage or a progressive functional deterioration, which fails to correct the decline of stroke volume in the long term, leading to progressive heart failure (HF). Surgical ventricular reconstruction (SVR) is a treatment for patients with severe ischemic HF aiming to restore LV efficiency by volume reduction and LV re-shaping. Recently, a new minimally-invasive hybrid technique for ventricular reconstruction has been developed by means of the Revivent (TM) system (BioVentrix Inc., San Ramon, CA, USA). The device for ventricular reconstruction consists of anchor pairs that enable plication of the anterior and free wall LV scar against the right ventricular (RV) septal scar of anteroseptal infarctions to decrease cardiac volume without ventriculotomy in a beating-heart minimally-invasive procedure, consisting of a transjugular and left thoracotomy approach. Patients with severe (Grade 4) functional mitral regurgitation (FMR) or with previous cardiac surgery procedures were excluded. Outcome of the reconstruction procedure: from 2012 until 2019, it has been applied to 203 patients, with 5 (2.5%) in-hospital deaths. LV volume reduction varied according to experience gained along years: LV end-systolic volume index decreased from baseline 43% (post-market registry) vs. 27% (CE-mark study); left ventricular ejection fraction (LVEF) increased from baseline 25% (post-market registry) vs. 16% (CE-mark study). Clinical status (NYHA class, HF questionnaire, 6-minute walking test) improved significantly compared to baseline, and re-hospitalization rate was only 13% at 6-month follow-up (60% of patients in NYHA =3). FMR grade decreased at follow-up in 63%, while it was unchanged in 37% of patients. The hybrid ventricular reconstruction (HVR) seems a promising treatment for HF patients who may benefit from LV volume reduction, with reasonable mortality and good results at follow-up. A baseline less severe clinical profile was not associated to better outcome at follow-up, which makes the procedure feasible in patients with very large ventricles and depressed ejection fraction (EF). LV reshaping has no detrimental effect on FMR, that may, on the contrary, benefit owing to less papillary muscle displacement, partial recovery of torsion dynamics and of myofibers re-orientation. A controlled study on top of optimal medical treatment is warranted to confirm its role in the management of HF patients
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
Pilot study on the separability of the native heart sounds and device support noise in patients implanted with left ventricular assist devices
Full text linkThe assessment of heart sounds in patients with Left Ventricular Assist Devices (LVADs) presents significant challenges. The persistent mechanical hum produced by the pump obscures the natural heart sounds, complicating the detection of critical issues such as valve dysfunction, suction events, and abnormal blood flow patterns. Currently, echocardiography is frequently employed for monitoring; however, its application is not practical for home environments. This study explores the potential of phonocardiography (PCG) as a non-invasive method for monitoring cardiac function in patients with LVADs, specifically by accurately estimating cardiac time intervals (CTIs). PCG signals were collected from patients equipped with the HM3 LVAD, AbbottTM. We employed Power Spectral Density (PSD) and Time-Frequency (TF) analysis to identify the dominant frequency components produced by the pump and their respective timings. A template-matching technique was applied to isolate the pulsatility mode of the LVAD from the PCG, thereby enabling the detection of native heart sounds. From this refined signal, we extracted the closure times of the heart valves. Our approach successfully differentiated native heart sounds from the in-band noise generated by the device, demonstrating the efficacy of PCG in LVAD patients. The identified CTIs provide important insights into the heart's compensatory mechanisms under these conditions and hold promise for continuous, non-invasive cardiac monitoring. This study presents the significant potential of PCG as an alternative to echocardiography for evaluating cardiac health in LVAD patients. Future research should focus on refining automated detection algorithms and validating this technique across larger patient populations to enhance its feasibility for monitoring in home settings.Clinical Relevance- This study provides clinicians with a non-invasive method to assess cardiac function in LVAD patients, overcoming issues from pump noise. Phonocardiography helps detecting complications early and reduces reliance on echocardiography, allowing for easier home monitoring and improved patient management
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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