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Search Results: 1 - 10 of 201512 matches for " Dimitri P Mikhailidis "
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Estimated Glomerular Filtration rate (eGFR): A Serum Creatinine-Based Test for the Detection of Chronic Kidney Disease and its Impact on Clinical Practice
Anjly Jain,Dimitri P. Mikhailidis,Devaki R. Nair
Oman Medical Journal , 2012,
The mechanisms of atrial fibrillation in hyperthyroidism
Agata Bielecka-Dabrowa, Dimitri P Mikhailidis, Jacek Rysz, Maciej Banach
Thyroid Research , 2009, DOI: 10.1186/1756-6614-2-4
Abstract: Atrial fibrillation (AF) is a common dysrrhythmia representing an independent risk factor for cardiovascular events [1]. The rapid and irregular heartbeat produced by AF increases the risk of blood clot formation inside the heart. These clots may eventually become dislodged, causing embolism, stroke and other disorders [1,2]. AF is a complex disease with several possible mechanisms. Studies indicate that arrhythmogenic foci within the thoracic veins can be AF initiators [2]. Once initiated, AF alters atrial electrical and structural properties in a way that promotes its own maintenance; this increases the risk of recurrence and may alter the response to antiarrhythmic drugs [2,3]. AF may occur in patients with a variety of cardiovascular or chronic diseases as well as in normal subjects. It is the most common cardiac complication of hyperthyroidism [3]. AF in thyrotoxicosis is associated with significant mortality and morbidity resulting from embolic events [3]. The risk factors for AF in patients with hyperthyroidism (age, male sex, ischemic heart disease, congestive heart failure and valvular heart disease) are similar to those in the general population [4]. AF occurs in up to 15% of patients with hyperthyroidism [5] compared with 4% incidence in the general population [6] and is more common in men and in patients with triiodothyronine (T3) toxicosis [3]. Also, subclinical hyperthyroidism is a risk factor that is associated with a 3-fold increase in risk of developing AF [5]. AF incidence increases with advancing age. Although it is rare in patients under 40 years of age, 25% to 40% of hyperthyroid individuals over the age of 60 experience AF, possibly reflecting an age-related reduction in threshold for acquiring this arrhythmia. Of hyperthyroid patients older than 60 years, 25% had AF compared with 5% prevalence in patients younger than 60 years [7]. Patients with toxic nodular goiter also showed, because of their age, an increased prevalence of AF versus younge
Lipoprotein Subfractions in Metabolic Syndrome and Obesity: Clinical Significance and Therapeutic Approaches
Dragana Nikolic,Niki Katsiki,Giuseppe Montalto,Esma R. Isenovic,Dimitri P. Mikhailidis,Manfredi Rizzo
Nutrients , 2013, DOI: 10.3390/nu5030928
Abstract: Small, dense low density lipoprotein (sdLDL) represents an emerging cardiovascular risk factor, since these particles can be associated with cardiovascular disease (CVD) independently of established risk factors, including plasma lipids. Obese subjects frequently have atherogenic dyslipidaemia, including elevated sdLDL levels, in addition to elevated triglycerides (TG), very low density lipoprotein (VLDL) and apolipoprotein-B, as well as decreased high density lipoprotein cholesterol (HDL-C) levels. Obesity-related co-morbidities, such as metabolic syndrome (MetS) are also characterized by dyslipidaemia. Therefore, agents that favourably modulate LDL subclasses may be of clinical value in these subjects. Statins are the lipid-lowering drug of choice. Also, anti-obesity and lipid lowering drugs other than statins could be useful in these patients. However, the effects of anti-obesity drugs on CVD risk factors remain unclear. We review the clinical significance of sdLDL in being overweight and obesity, as well as the efficacy of anti-obesity drugs on LDL subfractions in these individuals; a short comment on HDL subclasses is also included. Our literature search was based on PubMed and Scopus listings. Further research is required to fully explore both the significance of sdLDL and the efficacy of anti-obesity drugs on LDL subfractions in being overweight, obesity and MetS. Improving the lipoprotein profile in these patients may represent an efficient approach for reducing cardiovascular risk.
Sex-associated effect of CETP and LPL polymorphisms on postprandial lipids in familial hypercholesterolaemia
Katherine K Anagnostopoulou, Genovefa D Kolovou, Peggy M Kostakou, Constantinos Mihas, Georgios Hatzigeorgiou, Christina Marvaki, Dimitrios Degiannis, Dimitri P Mikhailidis, Dennis V Cokkinos
Lipids in Health and Disease , 2009, DOI: 10.1186/1476-511x-8-24
Abstract: We selected and genotyped 80 men and postmenopausal women heterozygous for familial hypercholesterolaemia (main group) as well as 11 healthy control subjects. Patients were subgrouped based on their response to oral fat tolerance test. The oral fat tolerance test was defined as pathological when postprandial triglyceride concentration was higher than the highest triglyceride concentration observed in healthy subjects (220 mg/dl) at any time (2, 4, 6 or 8 h).In the pathological subgroup, men had significantly higher incremental area under the curve after oral fat tolerance test than postmenopausal women. Furthermore, multivariate analysis revealed a gender association of TaqIB and I405V influence on postprandial lipaemia in this subgroup.In conclusion, it seems that gender and TaqIB polymorphism of the cholesteryl ester transfer protein gene were both associated with the distribution of triglyceride values after oral fat tolerance test, only in subjects with a pathological response to oral fat tolerance test. Specifically, men carrying the B2 allele of the TaqIB polymorphism showed a higher postprandial triglyceride peak and a delayed return to basal values compared with women carrying B2. However, further investigations in larger populations are required to replicate and confirm these findings.The mechanisms that control the cholesteryl ester transfer protein (CETP) have attracted attention, since plasma CETP concentration is associated with increased risk for premature atherosclerosis [1]. The CETP concentration and activity in plasma is dependent on several factors such as environmental components including dietary cholesterol [2], alcohol [3], smoking and obesity [4], gender [5], and genetic influence (e.g. polymorphism of CETP gene) [6-8]. CETP plays a major role in the remodeling of lipoprotein particles by mediating the transfer of high density lipoprotein (HDL) cholesteryl esters. When the level of triglyceride (TG)-rich lipoproteins is normal, CETP transfers
Incremental Aggregated Proximal and Augmented Lagrangian Algorithms
Dimitri P. Bertsekas
Mathematics , 2015,
Abstract: We consider minimization of the sum of a large number of convex functions, and we propose an incremental aggregated version of the proximal algorithm, which bears similarity to the incremental aggregated gradient and subgradient methods that have received a lot of recent attention. Under cost function differentiability and strong convexity assumptions, we show linear convergence for a sufficiently small constant stepsize. This result also applies to distributed asynchronous variants of the method, involving bounded interprocessor communication delays. We then consider dual versions of incremental proximal algorithms, which are incremental augmented Lagrangian methods for separable equality-constrained optimization problems. Contrary to the standard augmented Lagrangian method, these methods admit decomposition in the minimization of the augmented Lagrangian, and update the multipliers far more frequently. Our incremental aggregated augmented Lagrangian methods bear similarity to several known decomposition algorithms, including the alternating direction method of multipliers (ADMM) and more recent variations. We compare these methods in terms of their properties, and highlight their potential advantages and limitations. We also address the solution of separable inequality-constrained optimization problems through the use of nonquadratic augmented Lagrangiias such as the exponential, and we dually consider a corresponding incremental aggregated version of the proximal algorithm that uses nonquadratic regularization, such as an entropy function. We finally propose a closely related linearly convergent method for minimization of large differentiable sums subject to an orthant constraint, which may be viewed as an incremental aggregated version of the mirror descent method.
Centralized and Distributed Newton Methods for Network Optimization and Extensions
Dimitri P. Bertsekas
Mathematics , 2015,
Abstract: We consider Newton methods for common types of single commodity and multi-commodity network flow problems. Despite the potentially very large dimension of the problem, they can be implemented using the conjugate gradient method and low-dimensional network operations, as shown nearly thirty years ago. We revisit these methods, compare them to more recent proposals, and describe how they can be implemented in a distributed computing system. We also discuss generalizations, including the treatment of arc gains, linear side constraints, and related special structures.
Value and Policy Iteration in Optimal Control and Adaptive Dynamic Programming
Dimitri P. Bertsekas
Mathematics , 2015,
Abstract: In this paper, we consider discrete-time infinite horizon problems of optimal control to a terminal set of states. These are the problems that are often taken as the starting point for adaptive dynamic programming. Under very general assumptions, we establish the uniqueness of solution of Bellman's equation, and we provide convergence results for value and policy iteration.
Incremental Gradient, Subgradient, and Proximal Methods for Convex Optimization: A Survey
Dimitri P. Bertsekas
Mathematics , 2015,
Abstract: We survey incremental methods for minimizing a sum $\sum_{i=1}^mf_i(x)$ consisting of a large number of convex component functions $f_i$. Our methods consist of iterations applied to single components, and have proved very effective in practice. We introduce a unified algorithmic framework for a variety of such methods, some involving gradient and subgradient iterations, which are known, and some involving combinations of subgradient and proximal methods, which are new and offer greater flexibility in exploiting the special structure of $f_i$. We provide an analysis of the convergence and rate of convergence properties of these methods, including the advantages offered by randomization in the selection of components. We also survey applications in inference/machine learning, signal processing, and large-scale and distributed optimization.
Lambda-Policy Iteration: A Review and a New Implementation
Dimitri P. Bertsekas
Mathematics , 2015,
Abstract: In this paper we discuss $\l$-policy iteration, a method for exact and approximate dynamic programming. It is intermediate between the classical value iteration (VI) and policy iteration (PI) methods, and it is closely related to optimistic (also known as modified) PI, whereby each policy evaluation is done approximately, using a finite number of VI. We review the theory of the method and associated questions of bias and exploration arising in simulation-based cost function approximation. We then discuss various implementations, which offer advantages over well-established PI methods that use LSPE($\l$), LSTD($\l$), or TD($\l$) for policy evaluation with cost function approximation. One of these implementations is based on a new simulation scheme, called geometric sampling, which uses multiple short trajectories rather than a single infinitely long trajectory.
Increased Serum Levels of Uric Acid Are Associated with Sudomotor Dysfunction in Subjects with Type 2 Diabetes Mellitus
N. Papanas,M. Demetriou,N. Katsiki,K. Papatheodorou,D. Papazoglou,T. Gioka,S. Kotsiou,E. Maltezos,D. P. Mikhailidis
Experimental Diabetes Research , 2011, DOI: 10.1155/2011/346051
Abstract: The aim of this paper was to assess serum uric acid (SUA) levels in patients with type 2 diabetes mellitus (T2DM) with or without sudomotor dysfunction (evaluated by the Neuropad test). We included 36 T2DM patients with sudomotor dysfunction (group A: mean age 63.1±2.6 years) and 40 age-, gender-, renal function- and T2DM duration-matched patients without sudomotor dysfunction (group B: mean age 62.1±3.1 years). SUA was significantly higher in group A (<0.001). There was a significant correlation between SUA and Neuropad time to colour change in both groups (group A: =0.819, <0.001; group B: =0.774, <0.001). There was also a significant positive correlation between SUA and CRP in both groups (group A: =0.947, <0.001; group B: =0.848, <0.001). In conclusion, SUA levels were higher in T2DM patients with sudomotor dysfunction than those without this complication. The potential role of SUA in sudomotor dysfunction merits further study.
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