Search results for "Heart"
showing 10 items of 3201 documents
Foetal ECG recovery using dynamic neural networks
2002
Non-invasive electrocardiography has proven to be a very interesting method for obtaining information about the foetus state and thus to assure its well-being during pregnancy. One of the main applications in this field is foetal electrocardiogram (ECG) recovery by means of automatic methods. Evident problems found in the literature are the limited number of available registers, the lack of performance indicators, and the limited use of non-linear adaptive methods. In order to circumvent these problems, we first introduce the generation of synthetic registers and discuss the influence of different kinds of noise to the modelling. Second, a method which is based on numerical (correlation coe…
A Novel Approach to Propagation Pattern Analysis in Intracardiac Atrial Fibrillation Signals
2010
The purpose of this study is to investigate propagation patterns in intracardiac signals recorded during atrial fibrillation (AF) using an approach based on partial directed coherence (PDC), which evaluates directional coupling between multiple signals in the frequency domain. The PDC is evaluated at the dominant frequency of AF signals and tested for significance using a surrogate data procedure specifically designed to assess causality. For significantly coupled sites, the approach allows also to estimate the delay in propagation. The methods potential is illustrated with two simulation scenarios based on a detailed ionic model of the human atrial myocyte as well as with real data recordi…
A new Frequency Domain Measure of Causality based on Partial Spectral Decomposition of Autoregressive Processes and its Application to Cardiovascular…
2019
We present a new method to quantify in the frequency domain the strength of directed interactions between linear stochastic processes. This issue is traditionally addressed by the directed coherence (DC), a popular causality measure derived from the spectral representation of vector autoregressive (AR) processes. Here, to overcome intrinsic limitations of the DC when it needs to be objectively quantified within specific frequency bands, we propose an approach based on spectral decomposition, which allows to isolate oscillatory components related to the pole representation of the vector AR process in the Z-domain. Relating the causal and non-causal power content of these components we obtain…
A study on the effect of contact pressure during physical activity on photoplethysmographic heart rate measurements
2020
Heart rate (HR) as an important physiological indicator could properly describe global subject&rsquo
Automatic detection of cardiac contours on MR Images using fuzzy logic and dynamic programming
1997
International audience; Abstract: This paper deals with the use of fuzzy logic and dynamic programming in the detection of cardiac contours in MR Images. The definition of two parameters for each pixel allows the construction of the fuzzy set of the cardiac contour points. The first parameter takes into account the grey level, and the second the presence of an edge. A corresponding fuzzy matrix is derived from the initial image. Finally, a dynamic programming with graph searching is performed on this fuzzy matrix. The method has been tested on several MR images and the results of the contouring were validated by an expert in the domain. This preliminary work clearly demonstrates the interes…
Fuzzy fault tree analysis in modern γ-ray industrial irradiator: Use of fuzzy version of HEART and CREAM techniques for human error evaluation
2008
As well known, the lack of accurate quantitative human reliability data is a serious limitation and source of uncertainty in risk assessment. Therefore, in the last years, many Authors suggested that the use of the fuzzy sets theory can fill up this gap, performing as useful tool when dealing with qualitative or vague information. In such a framework, the present paper refers to the obtained results by using Fuzzy Fault Tree analyses of accidental scenarios which entail the potential exposure of operators working in γ-ray irradiation industrial plant. For these analyses the HEART methodology, a first generation HRA (Human Reliability Analysis) method, has been employed to evaluate the proba…
Myocardial G Protein Receptor–Coupled Kinase Expression Correlates With Functional Parameters and Clinical Severity in Advanced Heart Failure
2010
In heart failure (HF), sympathetic hyperactivation induces deleterious effects in myocardial β-adrenergic signaling, with receptor down-regulation and desensitization mediated by G protein receptor-coupled kinases (GRKs). We hypothesised that changes in GRK isoforms may be associated with clinical status in advanced HF, using the Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) scale.We included 31 patients with advanced HF undergoing transplantation. According to INTERMACS profiles, mRNA and protein levels of GRK isoforms in left ventricular (LV) myocardium were analyzed and compared with nonfailing LV samples.In failing LV myocardium, GRK2 and GRK5 (but not G…
β2- and β1-Adrenoceptor Expression Exhibits a Common Regulatory Pattern With GRK2 and GRK5 in Human and Animal Models of Cardiovascular Diseases.
2015
To explore if genic expression of β(1)- or β(2)-adrenoceptors (ARs) exhibits a common regulatory pattern with G protein-coupled receptor kinase (GRK) 2, GRK3, or GRK5 expression, we determined messenger RNA levels for these genes in different tissues from human and animal models of cardiovascular disease. We measured genic expression by qRT polymerase chain reaction in the left and right ventricles or peripheral blood mononuclear cells from healthy (n = 21), hypertensive (n = 20), heart failure (n = 24), and heart transplanted patients (n = 17) or in left ventricle, peripheral blood mononuclear cells, and kidney from spontaneously hypertensive rats or L-N-methyl-arginine-induced hypertensiv…
Living with stress: regulation of antioxidant defense genes in the subterranean, hypoxia-tolerant mole rat, Spalax.
2011
Lack of oxygen is life threatening for most mammals. It is therefore of biomedical interest to investigate the adaptive mechanisms which enable mammalian species to tolerate extremely hypoxic conditions. The subterranean mole rat Spalax survives substantially longer periods of hypoxia than the laboratory rat. We hypothesized that genes of the antioxidant defense, detoxifying harmful reactive oxygen species generated during hypoxia and hyperoxia, are involved in Spalax underground adaptation. Using quantitative RT-PCR, we analyzed the mRNA expression levels of seven antioxidant defense genes (catalase, glutathione peroxidase 1, glutathione-S-transferase Pi1, heme oxygenase 1, superoxide dism…
Influence of contrast agent dose and image acquisition timing on the quantitative determination of nonviable myocardial tissue using delayed contrast…
2004
BACKGROUND: Delayed contrast-enhanced magnetic resonance imaging (ceMRI) has been shown to identify areas of irreversible myocardial injury due to infarction (MI) with high spatial resolution, allowing precise quantification of nonviable (hyperenhanced) myocardium. The aim of our study was to investigate the size of nonviable myocardium quantitatively as a function of time post-contrast when inversion time is held constant in patients post-myocardial infarction using two contrast agent (CA) doses. METHODS: Nine patients with chronic MI underwent two MR scans on a 1.5 Tesla system. Contrast-enhanced MRI data in two short-axis (SA) slices were continuously acquired until 40 minutes after CA i…