1,721,326 research outputs found
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
Clinical relevance of tricuspid regurgitation and its management
No full textTricuspid regurgitation (TR) is very common and is often found in patients with left-sided heart valve disease. Tricuspid annuloplasty (TA) is currently recommended for the treatment of significant TR. However, long-term survival benefit has not been established due to the high prevalence of postoperative residual TR and mortality. Accurate assessment of TR severity and detailed preoperative and postoperative risk evaluation are thus essential to identify high-risk patients and improve clinical outcome. The aim of the present thesis is to assess clinical relevance of TR and its management.
Chapter 2 evaluated the relationship between TR severity and detailed echocardiography parameters and liver stiffness in 131 patients with TR secondary to left-sided heart valve disease. Results showed that patients with severe TR had increased liver stiffness and higher prevalence of liver cirrhosis compared with those with mild-moderate TR. Further, the degree of TR, right atrial pressure and inferior vena cava (IVC) diameter were independently associated with elevated liver stiffness. Importantly, the presence of ≥0.4cm2 effective regurgitant orifice of TR and >2.15cm IVC diameter may predict the presence of liver cirrhosis in patients with TR.
Chapter 3 assessed the clinical prognostic value of two modified Model for End-stage Liver Disease (MELD) scores in 394 patients undergoing TA. Results demonstrated that patients with severe TR had higher percentage of hepatorenal dysfunction than those with mild-moderate TR. Preoperative MELD-XI and MELD-Albumin scores were independently associated with adverse outcome. Significant improvement of hepatorenal function at 1-year post-operation was noted in patients who had no adverse events but not in those who experienced adverse outcome.
Chapter 4 evaluated the prognostic role of red blood cell distribution width (RDW) in 172 patients who underwent concomitant TA during left-sided valve surgery. Results showed that preoperative RDW was independently associated with adverse events. Importantly, an RDW measurement ≥15.2% predicted 1-year adverse outcome with high negative predictive value (94.4%). Further, preoperative right ventricular end-diastolic area was closely associated with RDW.
Chapter 5 assessed the incidence of acute kidney injury (AKI) and its impact on clinical outcomes in 339 patients undergoing TA. Results demonstrated that the incidence of AKI, defined using RIFLE, AKIN and KDIGO criteria was 57%, 52% and 53% respectively. For short-term outcome, AKI defined by all three scoring systems was independently associated with major adverse cardiovascular events (MACE) and mortality. For outcome beyond 30 days, AKI by all three criteria was associated with MACE and heart failure; only AKI by AKIN and KDIGO, but not RIFLE, was independently associated with mortality.
Besides having higher incidence of AKI, pulmonary systolic artery pressure may remain high in patients underwent TA. Chapter 6 found that residual pulmonary hypertension (PHT) occurred in 43% of patients who underwent TA. Preoperative larger right ventricular geometry and tricuspid valve tethering area, and significant TR were associated with residual PHT. Importantly, the presence of mild residual PHT had a 4.9-fold risk and significant residual PHT had an 8.7-fold risk of adverse events compared with no residual PHT.published_or_final_versionMedicineDoctoralDoctor of Philosoph
Clinical relevance of tricuspid regurgitation in right ventricular pacing and left heart disease
No full textValvular heart disease is a relatively common type of heart disease found globally. Tricuspid regurgitation (TR) is a widespread concomitant consequence of valvular disease, especially in patients with left-sided heart valve disease. Tricuspid regurgitation caused by the right ventricle (RV) pacing has also received much attention in recent years. Massive and long-term existing TR among patients with heart failure may affect their prognosis as it causes chronic congestion and subsequent hepatorenal dysfunction. Tricuspid annuloplasty (TA) is currently the primary treatment for significant TR. To date, however, the deep mechanism of RV pacing-induced TR is unclear, and how to improve and prevent TR and extend long-term survival in double valve replacement (DVR) patients has not been well established. Therefore, the present thesis aims to assess the prevalence and management of TR in RV pacing and DVR patients.
Chapter 2 describes a prospective study of RV pacemaker lead-induced TR between right ventricular apex (RVA) pacing and non-right ventricular apex (non-RVA) pacing under the three-dimensional echocardiography (3DE). Echocardiography provides a crucial diagnosis method. A total of 284 patients were evaluated for the change of TR severity following permanent pacemaker implantation. Results showed that RVA pacing is associated with worsening of TR severity compared with non-RVA pacing (55.3% vs 44.7%, p = 0.01). RVA pacing was more likely to impinge the posterior leaflet, whereas non-RVA pacing was more likely to be positioned in the middle without the interference of any tricuspid valves (TVs). Under 3DE, Chapter 2 demonstrates that preferential lead impingement to the tricuspid valves may be one possible mechanism that could explain the higher frequency of TR in RVA pacing than in non-RVA pacing.
Chapter 3 evaluates the clinical prognostic value of two modified Model for End-stage Liver Disease (MELD) scores in 210 patients undergoing DVR surgery. Severe and chronic TR causes hepatic and renal dysfunction, and the modified MELD scores reflect the hepatorenal function. In clinical settings, the Model for End-stage Liver Disease eXcluding International normalised ratio (INR) (MELD-XI) scores and modified MELD scores with albumin replacing the international normalised ratio (MELD-Albumin) scores have been reported as predictors of adverse events in liver and heart diseases. In contrast, their predictive function in DVR patients has received less attention. Chapter 3 assessed the clinical prognostic value of modified MELD scores in DVR patients. The results showed that DVR-only patients have a higher risk of worsening TR than those receiving DVR combined TA and that significant preoperative TR was associated with 1-year adverse outcomes. Secondly, the MELD-XI and MELD-Albumin scores independently predicted adverse outcomes during the follow-up. Lastly, the MELD-Albumin scores provided incremental prognostic value to clinical parameters and the EuroSCORE II (net reclassification index = 0.34; p < 0.01). This outcome demonstrates that monitoring the modified MELD scores before surgery may provide helpful information for risk-stratification in DVR patients.
In conclusion, this thesis systematically evaluates the different RV pacing sites of lead-induced TR and monitor the modified MELD scores to stratify the risk before surgery in DVR patients.published_or_final_versionMedicineDoctoralDoctor of Philosoph
Bioengineered cardiac patches with decellularized placental scaffold and human induced pluripotent stem cells for myocardial repair
No full textMyocardial infarction (MI) is the leading cause of death worldwide. There are limited options clinically available for treatment of MI. The main barrier in developing curative therapeutics is largely from the limited regenerative capacity of adult cardiomyocytes (CMs). Recent advances in human tissue engineering and stem cell technology have provided some promising opportunities in developing novel therapeutics for MI. One of such approaches is the direct cellular transplantation of CMs differentiated from pluripotent stem cells (PSCs) to replace the damaged heart muscles. However, the therapeutic efficiency of this approach is limited due to the poor survival of transplanted CMs in the hostile microenvironment of the ischemic host heart tissue. In this study, we took a design of bioengineered cardiac patch (BCP) as a new strategy for myocardial repair. We engineered a novel BCP by using the extracellular matrix (ECM) from the decellularized placenta as a natural scaffold for CMs derived from human induced PSC (hiPSC).
The BCPs were created by seeding human induced pluripotent stem cell-derived cardiomyocyte (iPSC-CM) onto the decellularized placenta of rat. Extensive biochemical and electrophysiological analyses were performed to obtain the functional properties of these BCPs. The BCPs were then transplanted to the MI heart of rat model induced by permanent left descending coronary artery ligation. Cytokine profiling demonstrated that the decellularized placenta contains multiple growths and angiogenic factors that are crucial for the survival of the hiPSC-CM. Optical mapping analysis showed that the BCPs exhibited organized mechanical contraction and synchronized electrical propagation. The transplanted BCPs significantly improved left ventricular function of the infarcted hearts as determined by measuring maximal positive derivatives of left ventricular pressure, end-systolic pressure-volume relationship, left ventricular ejection fraction, and fractional shortening compared with the MI, MI+DP and MI+CM groups for four weeks follow-up. Histological examination revealed that engraftment of the BCP at the infarct zone decreased infarct size and increased cell retention and neovascularization compared with the MI, MI+DP and MI+CM groups.
This thesis highlights a critical design and creation of the functional BCPs based on decellularized placenta and hiPSC-CMs. Transplantation of the BCPs successfully restored the damaged heart function. Thus, the work presented in this thesis provides a novel and promising therapy for treatment of MI.published_or_final_versionMedicineDoctoralDoctor of Philosoph
Contemporary evaluation of cardiovascular manifestations and related outcomes in type 2 diabetes mellitus : 'cardiovascular imaging and big data'
No full textType 2 diabetes mellitus (T2DM) is a prevalent chronic disease that constitutes a significant healthcare burden due to its associated micro- and macrovascular complications. Although cardiovascular manifestations in T2DM have been explored by a variety of studies, this thesis further assesses the association of diabetic risk factors and novel biomarkers with diabetic cardiomyopathy using prospective echocardiography studies, as well as the pharmacological effect of sodium-glucose cotransporter 2 (SGLT2) inhibitors on cardiovascular related outcomes in T2DM.
This thesis is comprised of four sections. Section I introduces an overview of diabetes, diabetic complications, study population and research methods. Section II evaluates the cardiovascular manifestations, especially diabetic cardiomyopathy in patients with T2DM using transthoracic echocardiography. There was an increase in left ventricular (LV) hypertrophy (LVH), deterioration of systolic dysfunction and diastolic dysfunction from baseline to over 1-year follow-up. Women had a higher prevalence of LVH and diastolic dysfunction at baseline and follow-up compared with men. Moreover, Women, but not men, with pre-clinical diastolic dysfunction had a higher incidence of major adverse cardiovascular events (MACE) than those with normal diastolic function.
Section III investigates mechanisms associated with cardiovascular manifestations in T2DM. Chapter 4 evaluates the association of adipocyte fatty acid-binding protein (AFABP) with longitudinal changes to LV remodelling and diastolic dysfunction in T2DM. Results found sex-specific AFABP in the highest quartile at baseline was independently associated with increase in LVM and deterioration of diastolic dysfunction. Moreover, AFABP was independently associated with incident MACE in patients with T2DM. We likewise explored the association of thrombospodin-2 (TSP2), a matricellular protein promotes fibrosis and anti-angiogenesis, with longitudinal changes to LV structure and function in T2DM. Chapter 5 showed TSP2 was positively and independently associated with deterioration of diastolic dysfunction.
Section IV explores the cardiovascular related outcomes in T2DM using data retrieved from territory-wide database in Hong Kong. LVH and diastolic dysfunction predict incidence of heart failure (HF), which affects 9-22% of patients with T2DM. Similarly, chronic kidney disease (CKD) is another common complication in patients with T2DM, with over 30% of patients being affected by this comorbidity. We investigated the interplay of incident CKD and/or HF and their associations with prognostics in T2DM. Results found the time from baseline to incident CKD or HF was similar, while cardiorenal syndrome occurred soon after new-onset of CKD or HF. The presence of CKD or HF was associated with 3-fold risk of mortality, and concomitant CKD and HF (regardless of which comes first) was associated with 6-7-fold of mortality compared with CKD/HF-free status. SGLT2 inhibitors have been widely used due to its cardiorenal protective effect. we compared the risk of hyperkalemia, pneumonia and sepsis between new users of SGLT2 inhibitors and dipeptidyl peptidase 4 (DPP-4) inhibitors. The use of SGLT2 inhibitors was associated with a lower risk of severe hyperkalemia, hyperkalemia, new initiation of potassium binders, while it did not increase risk of hypokalemia, compared to DPP-4 inhibitors. Moreover, prescribing SGLT2 inhibitors was also independently associated with a lower risk of pneumonia, sepsis and related death, compared with DPP-4 inhibitors.published_or_final_versionMedicineDoctoralDoctor of Philosoph
Hypokalaemia in hypertensive patients : data-driven epidemiological insights and machine learning-based risk analysis
No full textHypertension, a leading risk factor for cardiovascular disease, is commonly managed with diuretic therapy. Diuretic-induced hypokalaemia, a well-recognised electrolyte imbalance, carries the risk of precipitate ventricular arrhythmias or even sudden death, potentially undermining the efficacy of diuretics in reducing cardiovascular morbidity and mortality. However, the burden of hypokalaemia is challenging to quantify due to its subtle or non-specific symptoms and the diverse characteristics of the patient population affected by this condition. A comprehensive understanding of its prevalence, risk factors, and management is, therefore, imperative. In exploring the intricate relationship between hypokalaemia and hypertension, this thesis addresses a critical research gap— quantifying the risk and identifying predictors of hypokalaemia among hypertensive patients, especially treated with diuretics. Through a series of data-driven investigations, this body of work synthesizes findings from national and territorial datasets and machine learning models to inform clinical strategies and patient management.
The initial investigation into hydrochlorothiazide use in the treatment of hypertension highlights a notable hypokalaemia prevalence of 12.6%, with demographic factors and treatment duration identified as significant risk contributors. A subsequent study on indapamide shows a low incidence of severe hypokalaemia, with less than 1% necessitating hospitalisation, predominantly occurring early in the treatment course. These findings underscore the importance of careful drug selection and monitoring practices in clinical protocols.
Diving deeper into predictive analytics, this thesis employed machine learning algorithms to the broader hypertensive cohort. The Random Forest algorithm, in particular, was found to outperform four other common algorithms in identifying key predictors of hypokalaemia, including but not limited to demographic factors, medication use, and comorbid conditions. For patients with concurrent cardiovascular disease, additional risk factors such as specific treatment regimens were identified. A derived nomogram from this model provides clinicians with a practical tool to effectively identify hypertensive individuals at risk of hypokalaemia. This predictive capability suggests a pathway for artificial intelligence-augmented risk stratification and personalised medicine approaches.
Moreover, the application of consensus clustering, an unsupervised machine learning method, reveals three distinct cluster subgroups within the hypokalaemic hypertensive population, each with unique clinical characteristics and differential mortality risks. Cluster 1 comprises younger patients with fewer comorbidities; Cluster 2 includes older patients with prevalent cardiovascular conditions and exhibits the highest all-cause mortality risk; Cluster 3 consists of the oldest patients, with a higher prevalence of arthritis and cancer, and the highest cardiovascular mortality risks. This nuanced classification not only delineates the heterogeneity of the condition but also signals the need for tailored management strategies to mitigate the identified elevated risks of all-cause and cardiovascular mortality.
Collectively, these studies aim to highlight the multifaceted nature of hypokalaemia in the context of hypertension. This thesis not only fills a crucial knowledge gap by providing robust epidemiological evidence and advanced analytical risk assessments but also advocates for an evolution in the management of hypertensive patients. Through strategic monitoring, individualised therapy, and the integration of innovative machine learning tools, practitioners are better equipped to navigate the complexities of hypokalaemia, ultimately improving patient outcomes.published_or_final_versionMedicineDoctoralDoctor of Philosoph
Lifestyle factors and novel biomarkers in cardiometabolic diseases
No full textCardiovascular diseases (CVDs) are the leading cause of death worldwide. Socioeconomic factors, obesity, unhealthy diet, smoking and genetic factors are known as CVD risk factors. Metabolic syndrome (MetS) has been found to significantly increase the risk of CVDs. According to recent guidelines, promoting lifestyle interventions and weight management is essential. The measurement of novel biomarkers including fibroblast growth factor 21 (FGF21), lipocalin-2 (LCN-2), cystatin C, beta-2 microglobulin (B2M) and neurofilament light chain (NfL) may also provide valuable support for assessing CVDs and MetS.
Four studies in this thesis used the data from the Shenzhen-Hong Kong United Network on Cardiovascular Disease (SHUN-CVD), which is a population-based study conducted in China. The first study explored the relationship between hypertension and a healthy lifestyle score, which was derived from 5 factors: smoking, alcohol consumption, physical activity, body mass index and diet. The risk of hypertension tended to decrease with an increase in the healthy lifestyle score. Abdominal obesity is a risk factor for diabetes. The second study found that waist circumference (WC) had a significant linear relationship with haemoglobin A1c and fasting plasma glucose in both men and women. The optimal cutoff values of WC indicating a haemoglobin A1c of 6.5% in men and women are 85 cm and 86 cm, respectively.
Serum levels of FGF21, LCN-2, cystatin C and B2M were measured in the SHUN-CVD. The third study revealed that serum FGF21 was associated with systolic and diastolic blood pressure. A robust association was observed between FGF21 and hypertension. Additionally, CVDs are prevalent in patients with chronic kidney disease. The fourth study investigated the relationship between renal biomarkers and stroke risk. There were nearly a quarter (24%) of participants had high stroke risk. Serum LCN-2, cystatin C and B2M, independent of age, were associated with stroke risk.
MetS has been associated with neurological disorders and NfL is a neuro-axonal biomarker. The fifth study further examined the relationship between serum Nfl and MetS in US adults by using data from the National Health and Nutrition Examination Survey. The level of serum Nfl was increased in participants with MetS. NfL was significantly associated with both the number of MetS components and MetS severity score.
This thesis has several clinical implications. Firstly, there is an inverse relationship between the healthy lifestyle score and hypertension risk, which reinforces the need to address lifestyle to lower the risk of hypertension. Secondly, addressing abdominal obesity issue is beneficial to individuals with diabetes. WC cutoff values of 85 cm for men and 86 cm for women are appropriate for recommendation to undergo diabetes screening. Thirdly, FGF21 is a potential biomarker for assessing hypertension. Fourthly, serum LCN-2, cystatin C and B2M may be novel biomarkers for clinicians to assess stroke risk. Fifthly, measuring NfL may help identify neuro-axonal damage in patients with MetS and highlight the need for risk factor modification.published_or_final_versionMedicineDoctoralDoctor of Philosoph
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