| Zugriffsnummer | 32965 |
| Dokumenttyp | Dissertation |
| Peer Review | unbekannt |
| Sprache | Englisch |
| Titel | Realistic models of the electrical excitation in the human heart and the determination of the cardiac magnetic field |
| Autor(in); Institution |
Fruhner, Stefan; 8.4, Mathematische Modellierung und Datenanalyse, PTB-Berlin
|
| Quelle/Jahr | (2014), 204 S. |
| Dissertationsvermerk | Dissertation, Technische Universität Berlin, 2014 |
| Persistent Identifier | |
| Verlag | Berlin: |
| Freie Schlagworte | Elektrokardiogram (EKG) ; Magnetkardiogram (MKG) ; realistische Herzmodellierung |
| Zusammenfassung | This work presents a computer model of the electrical excitation of the human heart. The mechanical motion that is necessary for the function as a pump for blood is triggered off by a wave of electrical excitation. Ionic currents are traversing along the cardiac muscle cells. The strong anisotropy of the cardiac conduction system is reflected by the elongated shape of these cells and the complex structure of their spatial distribution. According to their location within the cardiac muscle the cells show different electrical properties. Here, the distribution of these different cell types is investigated for generic geometries as well as for realistic cardiac models. Therefore, data are extracted from magnetic resonance images (MRI) in order to create a patient-specific model. In absence of experimental information models for the cell type distribution and the myocardial fibre orientation are developed. To account for the contraction of the cardiac muscle cells the local displacement field is determined from measurements. The effect of cardiac motion on calculated bio-signals as electrocardiograms (ECG) and magneto-cardiograms (MCG) is investigated by comparing two different states of contraction to a dynamic simulation approach. Therefore, existing methods for the numerical simulation of static model domains are extended by an interpolation method that interchanges the geometric model describing the current state of contraction during the course of an ongoing electrical excitation. The shape of the simulation domain renders the results obtained by numerical simulation. This is especially true for the ECG and the MCG. Events within these signals, which are connected to excitation and repolarisation of the cardiac tissue, are associated with the corresponding state of contraction. Namely, the QRS-complex is not realistically reflected using a static systolic model for the human heart. The amplitude of the T-wave is affected by a reduction when the geometrical model is of diastolic type. The dynamic approach accounts for both effects. Measurements of the magneto-cardiogram are digitally processed. A model of the measurement device is built in order to calculate the corresponding signals from simulations of cardiac excitation. The geometrical model is successfully extended into three dimensions in order to find good agreement to the experimental data. The path of initial excitation cannot be determined from the experimental data. Therefore, it is investigated by comparing the magneto-cardiogram obtained from modelling different protocols of stimulation to the corresponding measurement results. It is shown that the site of initial stimulation strongly influences the morphology of the magnetocardiogram. The investigations indicate that the Purkinje fibre system must be incorporated into the model in order to accurately reproduce the MCG. |
