Search results for "Models"
showing 10 items of 8211 documents
Dofetilide effects on the inhibition by trains of subthreshold conditioning stimuli.
2004
We investigated the electrophysiological actions of dofetilide upon the ventricular myocardium to determine whether the drug modifies the inhibitory effects of subthreshold stimuli trains upon ventricular refractoriness. In nine Langendorff perfused rabbit hearts, ventricular epicardial electrodes were used to determine the following parameters at baseline and during dofetilide perfusion (0.5 micromolar): effective (ERP) and functional (FRP) refractory periods, conduction velocity (CV), wavelength (WL), and ERP prolongation (inhibitory effect) induced by subthreshold stimuli trains (STr) at pulse frequencies of 100, 300, and 600 Hz. Dofetilide significantly prolongs ventricular refractorine…
A mathematical model of cardiovascular dynamics for the diagnosis and prognosis of hemorrhagic shock
2020
Abstract A variety of mathematical models of the cardiovascular system have been suggested over several years in order to describe the time-course of a series of physiological variables (i.e. heart rate, cardiac output, arterial pressure) relevant for the compensation mechanisms to perturbations, such as severe haemorrhage. The current study provides a simple but realistic mathematical description of cardiovascular dynamics that may be useful in the assessment and prognosis of hemorrhagic shock. The present work proposes a first version of a differential-algebraic equations model, the model dynamical ODE model for haemorrhage (dODEg). The model consists of 10 differential and 14 algebraic e…
Second report on chicken genes and chromosomes 2005.
2005
International audience
Cost Effectiveness of Peginterferon ??-2a Plus Ribavirin versus Interferon ??-2b Plus Ribavirin as Initial Therapy for Treatment-Naive Chronic Hepati…
2004
Introduction: In adults with previously untreated chronic hepatitis C (CHC), the combination of peginterferon α-2a plus ribavirin produces a higher rate of sustained virological response (SVR) than interferon α-2b plus ribavirin, but it is still unproven whether this increase is cost effective. The objective of this study was to determine if the gain in SVR with peginterferon α-2a plus ribavirin is worth the incremental cost. Methods: We constructed a Markov model of disease progression in which cohorts of patients received peginterferon α-2a plus ribavirin or interferon α-2b plus ribavirin for 48 weeks (hepatitis C virus [HCV] genotype 1 and non-1 patients with fibrosis) or 24 weeks (genot…
A Multi-Variate Predictability Framework to Assess Invasive Cardiac Activity and Interactions during Atrial Fibrillation
2017
Objective: This study introduces a predictability framework based on the concept of Granger causality (GC), in order to analyze the activity and interactions between different intracardiac sites during atrial fibrillation (AF). Methods: GC-based interactions were studied using a three-electrode analysis scheme with multi-variate autoregressive models of the involved preprocessed intracardiac signals. The method was evaluated in different scenarios covering simulations of complex atrial activity as well as endocardial signals acquired from patients. Results: The results illustrate the ability of the method to determine atrial rhythm complexity and to track and map propagation during AF. Conc…
Artefacts in CBCT: a review
2011
Artefacts are common in today's cone beam CT (CBCT). They are induced by discrepancies between the mathematical modelling and the actual physical imaging process. Since artefacts may interfere with the diagnostic process performed on CBCT data sets, every user should be aware of their presence. This article aims to discuss the most prominent artefacts identified in the scientific literature and review the existing knowledge on these artefacts. We also briefly review the basic three-dimensional (3D) reconstruction concept applied by today's CBCT scanners, as all artefacts are more or less directly related to it.
Variations in acoustical beam properties of intracoronary Doppler catheters.
1993
The limitations of coronary angiography in assessing the functional significance of coronary obstructions is well known. While the critical variable of coronary blood flow cannot be readily measured, intraluminal Doppler sonography offers useful related functional information on blood flow velocity. In order to fully evaluate Doppler signals it is essential to have exact knowledge of the transducer transmission characteristics and of the ultrasound beam topology. In an experimental set-up, the transmitter-receiver characteristics of five commonly used Doppler catheters were investigated. In comparing the beam characteristics we found inhomogeneities in the lateral beam spread. At a penetrat…
Cost-effectiveness analysis of robot-assisted vs. open partial nephrectomy
2017
Background The cost-effectiveness of robot-assisted partial nephrectomy (RAPN) vs. the open procedure is not established. Methods We estimated in-hospital complications and the cost of RAPN vs. open partial nephrectomy (OPN) using an economic model. Costs incurred both intraoperatively and in hospital were considered. US data were extracted from existing literature. Results Mean in-hospital costs were $14,824 (95% CI $13,368-$16,898) for RAPN and $15,094 (95% CI $13,491-$17,140) for OPN. Complications after RAPN occurred in 23.3% (95% CI 20.0-25.8%) and after OPN in 36.1% (95% CI 35.6-36.6%) of the patients. In a sensitivity analysis, limited centre experience was associated with relevant i…
Size and subclasses of low-density lipoproteins in patients with obstructive sleep apnea.
2012
Patients with obstructive sleep apnea (OSA) have proatherogenic dyslipidemia. We analyzed predictors of low-density lipoproteins' (LDLs) size in patients with OSA. In a cross-sectional study including 58 participants with OSA (30 without the metabolic syndrome [MetS] and 28 with MetS), we evaluated the size of LDL by gradient gel electrophoresis. Compared with patients without the MetS, those with MetS showed lower LDL size ( P = .007), due to a reduction in large LDL-I particles ( P = .002) and an increase in small, dense LDL-IIIA ( P = .048) and LDL-IIIB ( P = .037). The size of LDL correlated inversely with age ( r = −.268, P = .042) and serum triglycerides ( r = −.364, P = .005), and p…
Associated factors to psychiatric morbidity in postmenopausal phases.
1998
Abstract Background: The greatest risk of psychiatric morbidity during the climacteric years is linked to a greater exposure to stressful life experiences, women's dissatisfaction with their role in society and to an absence of social backup. The question to be posed now is the extent to which the longitudinal surveys can confirm, refute or complement the results of the cross-sectional analyses. Methods: A study involving population-based cohorts was carried out on a sample of 120 women who had been previously identified as being premenopausal or menopausal during a cross-sectional examination conducted between 1987 and 1988 within the city of Valencia (Spain). The aims were to analyze the …