Whole heart modeling: from validation of animal experiments to the reconstruction of the human magnetocardiogram

Our interest in heart modeling is on one hand strongly motivated by the desire to compare cardiac simulation results with data obtained from magnetocardiogram (MCG) measurements of human beings and animals in various setups. On the other hand, we have started to integrate imaging data at various levels in our modeling approach. In the first part, we report in detail on simulations of anatomically realistic models for animal ventricles using the modified Beeler-Reuter ionic model and compare these with experimental data. Simulations of a rabbit heart were carried out and compared with experiments in Langendorff perfusion. The time evolution of the spatial profiles of the extracellular potential on the surface of the rabbit heart was correctly reproduced. The effects of ajmaline (Na-channel blockage) and palmitoleic acid (decrease of intracellular conductivity) were included subsequently in the model. In addition, pacing simulations of the ventricles have been performed using different frequencies. Occurrence of action potential duration alternans was found for frequencies greater than 230 bpm. Fibrillation occurred for frequencies greater than 260 bpm. Finally, the influence of geometry change during the human heart beat on MCG signals was investigated. We computed the MCG using the ten Tusscher ionic model for 2-dimensional cuts through the ventricles recorded by magnetic resonance imaging during systole resp. diastole and found a much shorter QRS for the diastolic geometry. Furthermore, the dynamic geometry of the heart was recorded and translated into a moving finite element mesh used in 3-dimensional simulations of the heart.