Aniceto Silva

Left atrial volume calculated by multi-detector computed tomography may predict successful pulmonary vein isolation in catheter ablation of atrial fibrillation

AIMS Catheter ablation (CA) of atrial fibrillation (AF) might be a definitive curative therapy for selected groups of patients (pts). However, current ablation protocols are not standardized and predictors of CA success and sinus rhythm maintenance are not clearly defined. To evaluate whether left atrium (LA) volume quantification provided by multi-detector computed tomography (MDCT) might predict the success of pulmonary vein (PV) isolation procedure. METHODS AND RESULTS We evaluated 99 pts, 66 male, mean age 54.4 +/- 10.1 years, referred for CA because of drug resistant AF. All pts were submitted to 64-slice MDCT scan for electroanatomic mapping integration, pulmonary veins anatomy delineation, LA thrombi exclusion, and LA volume estimation. Complete isolation of all the PVs was always performed with eventual cavo-tricuspid isthmus ablation. For a mean follow-up period (Fup) of 16.7 +/- 6.6 months, clinical success was assessed after a 3-month blanking period. Anti-arrhythmic drug therapy was discontinued or modified at the clinicians criteria. At the end of the Fup, 29 pts suspended anti-arrhythmic drug therapy and 26% were of oral anticoagulation. Univariate analysis showed that the probability of AF relapse after CA was higher in pts with non-paroxysmal forms of AF. The probability of relapse was significantly higher in pts with LA volumes greater than 100 mL when assessed by MDCT. We found that the LA volume of 145 mL was a good cut-off value for AF recurrence prediction. Patients with LA volumes greater than 145 mL had significantly higher recurrence rates of arrhythmia, even when adjusted for the effect of age, gender, body mass index, hypertension, and type of AF. CONCLUSION Left atrium volume estimated by MDCT may be useful to identify pts in whom successful AF ablation can be achieved with simpler ablation procedures, restricted to PV isolation.

Engineering aspects of the tokamak ISTTOK

AbstractThe first Portuguese magnetic confinement experiment, the tokamak ISTTOK, has been in operation since 1993. This tokamak device is described and the main technological features, as well as the novel techniques of its diagnostics and control and data acquisition system, are reported. A synopsis of the experimental activity is also presented.

Application of the Factor Method to the Prediction of the Service Life of Ceramic External Wall Cladding

AbstractThe main goal of this study is to use the factor method to evaluate the service life of ceramic external cladding. An interesting possibility is that a tool may be developed to aid the planning of maintenance operations, to reduce costs, and to ensure a better performance of the cladding system. The method relies on field work data on the state of repair of the facades, based on a survey of 195 facades in the Lisbon area. The factors affecting durability are singled out and quantified through several scenarios with the aim of optimizing the weighting coefficients. The degradation model has provided consistent results for most of the variables influencing the cladding’s loss of performance. Adequate knowledge on the durability of a component allows correctly designing the details and planning the maintenance operations that the component requires. These in turn are part of a broader perspective that involves reductions in costs and environmental impact, exactly the challenges that service life pred...

Does continuous ST-segment monitoring add prognostic information to the TIMI, PURSUIT, and GRACE risk scores?

Background: Recurrent ischemia is frequent in patients with non‐ST‐elevation acute coronary syndromes (NST‐ACS), and portends a worse prognosis. Continuous ST‐segment monitoring (CSTM) reflects the dynamic nature of ischemia and allows the detection of silent episodes. The aim of this study is to investigate whether CSTM adds prognostic information to the risk scores (RS) currently used.

A large area full-field EDXRF imaging system based on a THCOBRA gaseous detector

By taking advantage of the attractive features in terms of gain, position and energy resolution of the 2D-THCOBRA detector, a new large area Full-Field X-ray Fluorescence Imaging (FF-XRFI) system for EDXRF imaging applications was developed. The proposed FF-XRFI system has an active area of 10 × 10 cm2 and can be used to examine macroscopic samples with a moderately good energy resolution (<1.6 keV FWHM at 8 keV) and a suitable spatial resolution (∼500 μm FWHM). This combination of characteristics allows us to record elemental distribution maps from the surface of different sample types by combining image and energy information. Two different approaches were used for X-ray optics, one based on a single pinhole and another based on a parallel multiple-hole collimator. To illustrate the system capabilities, some sample examples were imaged and studied.

NT-proBNP na estratificação de risco no tromboembolismo pulmonar

INTRODUCTION Pulmonary embolism (PE) is an entity with high mortality and morbidity, in which risk stratification for adverse events is essential. N-terminal brain natriuretic peptide (NT-proBNP), a right ventricular dysfunction marker, may be useful in assessing the short-term prognosis of patients with PE. AIMS To characterize a sample of patients hospitalized with PE according to NT-proBNP level at hospital admission and to assess the impact of this biomarker on short-term evolution. METHODS We performed a retrospective analysis of consecutive patients admitted with PE over a period of 3.5 years. Based on the median NT-proBNP at hospital admission, patients were divided into two groups (Group 1: NT-proBNP<median and Group 2: NT-proBNP ≥ median). The two groups were compared in terms of demographic characteristics, personal history, clinical presentation, laboratory, electrocardiographic and echocardiographic data, drug therapy, in-hospital course (catecholamine support, invasive ventilation and in-hospital death and the combined endpoint of these events) and 30-day all-cause mortality. A receiver operating characteristic (ROC) curve was constructed to determine the discriminatory power and cut-off value of NT-proBNP for 30-day all-cause mortality. RESULTS Ninety-one patients, mean age 69±16.4 years (51.6% aged ≥75 years), 53.8% male, were analyzed. Of the total sample, 41.8% had no etiological or predisposing factors for PE and most (84.6%) were stratified as intermediate-risk PE. Median NT-proBNP was 2440 pg/ml. Patients in Group 2 were significantly older (74.8±13.2 vs. 62.8±17.2 years, p=0.003) and more had a history of heart failure (35.5% vs. 3.3%, p=0.002) and chronic kidney disease (32.3% vs. 6.7%, p=0.012). They had more tachypnea on initial clinical evaluation (74.2% vs. 44.8, p=0.02), less chest pain (16.1% vs. 46.7%, p=0.01) and higher creatininemia (1.7±0.9 vs. 1.1±0.5mg/dl, p=0.004). Group 2 also more frequently had right chamber dilatation (85.7% vs. 56.7%, p=0.015) and lower left ventricular ejection fraction (56.4±17.6% vs. 66.2±13.5%, p=0.036) on echocardiography. There were no significant differences in drug therapy between the two groups. Regarding the studied endpoints, Group 2 patients needed more catecholamine support (25.8% vs. 6.7%, p=0.044), had higher in-hospital mortality (16.1% vs. 0.0%, p=0.022) and more frequently had the combined endpoint (32.3% vs. 10.0%, p=0.034). All-cause mortality at 30 days was seen only in Group 2 patients (24.1% vs. 0.0%, p=0.034). By ROC curve analysis, NT-proBNP had excellent discriminatory power for this event, with an area under the curve of 0.848. The best NT-proBNP cut-off value was 4740 pg/ml. CONCLUSION Elevated NT-proBNP levels identified PE patients with worse short-term prognosis, and showed excellent power to predict 30-day all-cause mortality. The results of this study may have important clinical implications. The inclusion of NT-proBNP measurement in the initial evaluation of patients with PE can add valuable prognostic information.

THGEM gain calculations using Garfield++: solving discrepancies between simulation and experimental data

Discrepancies between the measured and simulated gain in Thick Micropatterned gaseous detectors (MPGD), namely THGEM, have been observed by several groups. In order to simulate the electron avalanches and the gain the community relies on the calculations performed in Garfield++, known to produce differences of 2 orders of magnitude in comparison to the experimental data for thick MPGDs. In this work, simulations performed for Ne/5%CH4, Ar/5%CH4 and Ar/30%CO2 mixtures shows that Garfield++ is able to perfectly describe the experimental data if Penning effect is included in the simulation. The comparison between the number of excitations which may lead to a Penning transfer, is shown for THGEM and GEM, explaining the less pronounced gain discrepancies observed in GEM.

X-ray imaging detector based on a position sensitive THCOBRA with resistive line

A new X-ray imaging detector based on a 2D-THCOBRA micropatterned structure using a simple position readout is proposed. It consists of a hybrid device that combines the prop- erties of a THGEM and a 2D-MHSP in a single structure, having two charge multiplication stages reaching the demanded gains for the use of charge division readout methods. For position determination, the new 10 10 cm 2 2D-THCOBRA structure uses two orthogonal resistive lines located at the end of the anode and top electrodes. The charge signal pulses collected at the end of each resistive line are digitized and processed in order to determine the center-of- gravity of the electron avalanche distribution. The detector uses a preamplification stage performed by a THGEM, followed by the 2D- THCOBRA, being operated in Ne/5%CH4 at atmospheric pressure. A characterization of the de- tector in terms of charge gain was made as a function of the voltage applied to the electrodes of the 2D-THCOBRA structure. The energy resolution of the system was also measured, envisaging Energy Weighting Technique (EWT) applications. The system characterization in terms of spatial resolution is presented together with imaging examples to evaluate its performance in X-ray imaging applications.

Fuzzy Systems in the Service-Life Prediction of Exterior Natural Stone Claddings

AbstractBuildings and their elements are designed to be used for a certain period of time (their service life), fulfilling all requirements for which they were designed without excessive maintenance costs. However, buildings begin to deteriorate because the instant they are put into use, they begin to show a progressive loss of performance until they become obsolete, having deteriorated beyond minimal acceptable levels or having failed to meet economic expectations. Nowadays, mostly for economic and environmental reasons, there is a growing concern about the durability and service life of buildings. This paper discusses the service life prediction of natural stone claddings using a Takagi-Sugeno fuzzy model. The models proposed include variables that influence the degradation of the claddings analyzed. To obtain the models proposed, samples of 140 and 203 facades were subjected to meticulous field work to determine their condition. The service life of the samples was also evaluated and the influence of th...

Stochastic Approach to the Factor Method: Durability of Rendered Façades

AbstractThe degradation of building materials occurs as a stochastic phenomenon. Service life prediction methods are usually divided into deterministic, stochastic, and engineering methods. Deterministic models are simpler and easier to use, but are unable to capture the random nature of the degradation phenomena. On the other hand, stochastic models are more complex but very efficient in dealing with the uncertainty associated with a building’s performance. In this study, a stochastic approach to the factor method is proposed to predict the service life of rendered facades. The model proposed is based on a survey of the degradation state of 85 rendered facades located in Portugal. The factors that affect the durability of this type of coating are identified and translated into probability distributions. This analysis leads to coherent values, revealing that facades on buildings built with adequate design measures are more durable; facades exposed to adverse environmental conditions are more prone to degr...