I. M. Graf, G. Seemann, D. L. Weiss, and O. Dössel. Influence of electrophysiological heterogeneity on electrical stimulation in healthy and failing human hearts. In Medical & Biological Engineering & Computing, vol. 43(6) , pp. 783-792, 2005
The application of strong electrical stimuli is a common method used for terminating irregular cardiac behaviour. The study presents the influence of electrophysiological heterogeneity on the response of human hearts to electrical stimulation. The human electrophysiology was simulated using the ten Tusscher-Noble-Noble-Panfilov cell model. The anisotropic propagation of depolarisation in three-dimensional virtual myocardial preparations was calculated using bidomain equations. The research was carried out on different types of virtual cardiac wedge. The selection of the modelling parameters emphasises the influence of cellular electrophysiology on the response of the human myocardium to electrical stimulation. The simulations were initially performed on a virtual cardiac control model characterised by electrophysiological homogeneity. The second preparation incorporated the transmural electrophysiological heterogeneity characteristic of the healthy human heart. In the third model type, the normal electrophysiological heterogeneity was modified by the conditions of heart failure. The main currents responsible for repolarisation (Ito, IKs and IKI) were reduced by 25%. Successively, [Na+]i was increased by the regulation of the Na+-Ca2+ exchange function, and fibrosis was represented by decreasing electrical conductivity. Various electrical stimulation configurations were used to investigate the differences in the responses of the three different models. Monophasic and biphasic electrical stimuli were applied through rectangular paddles and needle electrodes. A whole systolic period was simulated. The distribution of the transmembrane voltage indicated that the modification of electrophysiological heterogeneity induced drastic changes during the repolarisation phase. The results illustrated that each of the heart failure conditions amplifies the modification of the response of the myocardium to electrical stimulation. Therefore a theoretical model of the failing human heart must incorporate all the characteristic features.
G. Seemann, D. L. Weiß, F. B. Sachse, and O. Dössel. Electrophysiology and Tension Development in a Transmural Heterogeneous Model of the Visible Female Left Ventricle. In Lecture Notes in Computer Science, vol. 3504, pp. 172-182, 2005
K. Chaisaowong, F. B. Sachse, and G. Seemann. Modeling of human cardiac force development: I. Adjustment of an electrophysiological model to approach specimen-specific properties of myocytes. In Proc. 2nd ECTI Annual Conference, pp. 811-814, 2005
F. B. Sachse, G. Seemann, and B. Taccardi. Insights into Electrophysiological Studies with Papillary Muscle by Computational Models. In Lecture Notes in Computer Science, vol. 3504, pp. 216-225, 2005
D. L. Weiss, G. Seemann, and O. Dössel. Efficient Solving of Mathematical Models Describing the Behavior of Cardiac Myocytes. In Biomedizinische Technik, vol. 50(1) , pp. 566-567, 2005
D. L. Weiss, G. Seemann, and O. Dössel. Epicardial stimulation of a virtual left ventricular wall comprising heterogeneity and anisotropy. In Proc. IFMBE / EMBEC, vol. 11, 2005
D. L. Weiss, G. Seemann, F. B. Sachse, and O. Dössel. Epicardial Activation Increases Transmural Dispersion of Repolarization in a Heterogeneous Model of Wild-Type and Short QT Mutant Tissue. In Proc. Computers in Cardiology, vol. 32, pp. 117-120, 2005
G. Seemann. Modeling of electrophysiology and tension development in the human heart. Institut für Biomedizinische Technik. Dissertation. 2005
Comprehension of the beating of the human heart is important for cardiac research and will improve many clinical applications. Simulations based on models describing cardiac electro-mechanics can acquire insights into this behavior. This work focuses on the mathematical reconstruction of electrophysiology, excitation conduction, and tension development in the human heart on the cellular and the tissue level. The tissue models represent accurate anatomical shapes of the atria and the ventricles and incorporate electrophysiological heterogeneity and anisotropic conduction. The simulations comprehend the physiological behavior of the ventricles and of the atrium including the sinoatrial node as well as pathological cases like ventricular and atrial fibrillation and genetic defects in ionic channels.