Abstract: The forward problem of electrocardiography aims at obtaining a better understanding of cardiac electrophysiological activities, by means of computer modeling and simulation. Whereas, the inverse electrocardiographic problem provides a direct insight of electrical sources into the heart without interventional procedures. Nowadays, the forward and inverse problems are mostly solved in static models, which do not take into account heart motion and respiration. Besides heart motion, neglecting respiration may also lead to remarkable uncertainties in both forward and inverse solutions. In the present work a dynamic lung model is developed. With this model the effect of respiration on the forward and inverse solutions is studied.
Abstract: The post extrasystolic T wave change (PEST) is an electrocardiographic phenomenon in which the morphology of the normal T wave is altered for a short time after a ventricular ectopic beat (VEB). It has been observed in patients with other cardiac pathologies but it has not been proposed as a risk index for cardiac death. Since PEST seems to be potentiated in patients with depression of myocardial contractility, we hypothesize that PEST could be used to predict pump failure death (PFD) in patients with chronic heart failure (CHF). For the purpose of quantifying PEST, the parameters morphological change onset (MCO) and morphological change slope (MCS) were introduced.
The MUSIC study was used to test the hypothesis. The patients in the study were separated according to its cause of death and comparisons of each cause against the others (including survivors) were carried out. In addition, the parameters MCO and MCS were divided into subgroups us- ing optimal values obtained from the corresponding ROC curves with the aim of analyzing predictability with respect to PFD. The results showed that no significant differences could be established and the proposed parameters do not seem to be related to any kind of cardiac death.
R. Menges, G. Lenis, and O. Dössel. Choosing the best rhythmical and morphological features for a QRS complex classification algorithm.
In Biomedizinische Technik / Biomedical Engineering, vol. 59(s1) , pp. 185, 2014
Abstract: Ectopic beats are a common cause for cardiac arrhythmia. The methods presented in this paper deal with the evaluation of the features that are used by an existing classifier to distinguish between normal, supraventricular ectopic and ventricular ectopic beats. In order to classify the beats, a support vector machine (SVM) is used. Since noisy features can confuse the classifier and downgrade its performance, high quality features should be chosen. In the end, the performance should be improved by using only the selected features after the evaluation process. For this purpose, a receiver operating character- istic (ROC) analysis was conducted first. Secondly, the Gini diversity index (GDI) was calculated for every feature which is often used as split criterion in decision trees. As a third evaluation tool, the information gain ratio (IGR) was applied to estimate the quality of the features. To conclude the evaluation part, a fourth analysis was implemented. The ROC was applied again to the beats that are falsely classified in a first run-through. This was a first step into a deeper investigation of the dependency among features. As result of the evaluation process, a feature ranking was built and 36 of the 55 features were chosen to build the new SVM. A training and testing process was conducted using beats of the MIT-BIH-Arrhythmia- Database. A correct rate of 98.574%, a sensitivity of 98.592% and a positive predictive value of 99.062% were achieved.
Abstract: Anatomically realistic computational models provide a powerful platform for investigating mechanisms that underlie atrial rhythm disturbances. In recent years, novel techniques have been developed to construct structurally-detailed, image-based models of 3D atrial anatomy. However, computational models still do not contain full descriptions of the atrial intramural myofiber architecture throughout the entire atria. To address this, a semi-automatic rule-based method was developed for generating multi-layer myofiber orientations in the human atria. The rules for fiber generation are based on the careful anatomic studies of Ho, Anderson and co-workers using dissection, macrophotography and visual tracing of fiber tracts. Separately, a series of high color contrast images were obtained from sheep atria with a novel confocal surface microscopy method. Myofiber orientations in the normal sheep atria were estimated by eigen-analyis of the 3D image structure tensor. These data have been incorporated into an anatomical model that provides the quantitative representation of myofiber architecture in the atrial chambers. In this study, we attempted to compare the two myofiber generation approaches. We observed similar myo-bundle structure in the human and sheep atria, for example in Bachmann's bundle, atrial septum, pectinate muscles, superior vena cava and septo-pulmonary bundle. Our computational simulations also confirmed that the preferential propagation pathways of the activation sequence in both atrial models is qualitatively similar, largely due to the domination of the major muscle bundles.
Student Thesis (3)
Y. Meng. Auswirkungen der Modellierungsfehler auf die Lösung vom Vorwärts- und inversen Problem der Elektrokardiographie.
Institut für Biomedizinische Technik, Karlsruher Institut für Technologie (KIT). Studienarbeit. 2009