RESUMEN
Atherosclerotic plaques form at specific sites of the arterial tree, an observation that has led to the "geometric risk factor" hypothesis for atherogenesis. It is accepted that the location of atherosclerotic plaques is correlated with sites subjected to low abnormal values of wall shear stress (WSS), which is in turn determined by the specific geometry of the arterial segment. In particular, the left coronary artery (LCA) is one of the most important sites of plaque formation and its progression may lead to stroke. However, little is known about hemodynamics and WSS distributions in the LCA. The purpose of this work is to set up a method to evaluate flow patterns and WSS distributions in the human LCA based on real patient-specific geometries reconstructed from medical images.
Asunto(s)
Arterias/fisiopatología , Vasos Coronarios/fisiopatología , Estrés Fisiológico , Aterosclerosis/fisiopatología , Humanos , Modelos AnatómicosRESUMEN
Determination of the adequacy of dialysis is a routine but crucial procedure in patient evaluation. The total dialysis dose, expressed as Kt/V, has been widely recognised to be a major determinant of morbidity and mortality in haemodialysed patients. Many different factors influence the correct determination of Kt/V, such as urea sequestration in different body compartments, access and cardiopulmonary recirculation. These factors are responsible for urea rebound after the end of the haemodialysis session, causing poor Kt/V estimation. There are many techniques that try to overcome this problem. Some of them use analysis of blood-side urea samples, and, in recent years, on-line urea monitors have become available to calculate haemodialysis dose from dialysate-side urea kinetics. All these methods require waiting until the end of the session to calculate the Kt/V dose. In this work, a neural network (NN) method is presented for early prediction of the Kt/V dose. Two different portions of the dialysate urea concentration-time profile (provided by an on-line urea monitor) were analysed: the entire curve A and the first half B, using an NN to predict the Kt/V and compare this with that provided by the monitor. The NN was able to predict Kt/V is the middle of the 4h session (B data) without a significant increase in the percentage error (B data: 6.69% +/- 2.46%; A data: 5.58% +/- 8.77%, mean +/- SD) compared with the monitor Kt/V.
Asunto(s)
Monitoreo Fisiológico/instrumentación , Redes Neurales de la Computación , Diálisis Renal/normas , Urea/análisis , Adulto , Anciano , Femenino , Humanos , Masculino , Persona de Mediana Edad , Monitoreo Fisiológico/métodos , Resultado del TratamientoRESUMEN
Most systems for the automatic detection of abnormalities in the ECG require prior knowledge of normal and abnormal ECG morphology from pre-existing databases. An automated system for abnormality detection has been developed based on learning normal ECG morphology directly from the patient. The quantisation error from a self-organising map 'learns' the form of the patient's ECG and detects any change in its morphology. The system does not require prior knowledge of normal and abnormal morphologies. It was tested on 76 records from the European Society of Cardiology database and detected 90.5% of those first abnormalities declared by the database to be ischaemic. The system also responded to abnormalities arising from ECG axis changes and slow baseline drifts and revealed that ischaemic episodes are often followed by long-term changes in ECG morphology.
Asunto(s)
Electrocardiografía/métodos , Isquemia Miocárdica/diagnóstico , Procesamiento de Señales Asistido por Computador , Humanos , Redes Neurales de la ComputaciónRESUMEN
Total dialysis dose (Kt/V) is considered to be a major determinant of morbidity and mortality in hemodialyzed patients. The continuous growth of the blood urea concentration over the 30- to 60-min period following dialysis, a phenomenon known as urea rebound, is a critical factor in determining the true dose of hemodialysis. The misestimation of the equilibrated (true) postdialysis blood urea or equilibrated Kt/V results in an inadequate hemodialysis prescription, with predictably poor clinical outcomes for the patients. The estimation of the equilibrated postdialysis blood urea (eqU) is therefore crucial in order to estimate the equilibrated (true) Kt/V. In this work we propose a supervised neural network to predict the eqU at 60 min after the end of hemodialysis. The use of this model is new in this field and is shown to be better than the currently accepted methods (Smye for eqU and Daugirdas for eqKt/V). With this approach we achieve a mean difference error of 0.22 +/- 7.71 mg/ml (mean % error: 1.88 +/- 13.46) on the eqU prediction and a mean difference error for eqKt/V of -0.01 +/- 0.15 (mean % error: -0.95 +/- 14.73). The equilibrated Kt/V estimated with the eqU calculated using the Smye formula is not appropriate because it showed a great dispersion. The Daugirdas double-pool Kt/V estimation formula appeared to be accurate and in agreement with the results of the HEMO study.