Section: New Results

Modelling, direct simulation and prediction of cardiac phenomena

Using high-performance simulations on a detailed model of the human atria [58] we investigated several aspects of atrial fibrillation (AF). We showed that AF initiation by rapid pacing is sensitive to very small changes in parameter values [70] [32], [38] , and investigated effects of antiarrhythmic drugs and interventions [59] [34] and pathologies [35]. An example movie is available online at https://www.potse.nl/papers/potse/potse-fimh19.html.

High-performance simulations of human ventricular activity have contributed to the testing of new electrocardiographic mapping methods (“inverse models”) [73], [36].

We are also developing new methods to help with the treatment of these patients by rapidly guiding an ablation catheter to the origin (strictly speaking: the exit site) of an arrhythmia. These methods are also being tested with simulated data. [33].

We contributed to work by Prof. Michel Haissaguerre and his team in which it is argued that many patients who are now believed to suffer from abnormalities in the genes for specific cardiac ion channels are in reality affected by structural diseases of the heart muscle [62] [26], [41]. These influential publications represent an important change in thinking about these patients and their treatment.

Simple mitochondrial model based on thermodynamic fluxes (PhD work of B. Tarraf): Mitochondria are involved in the regulation of calcium which plays a crucial role in the propagation of cardiac action potentials. However, they are not taken into account in the ionic models that are used to perform simulations at the tissue level. In the framework of the ANR MITOCARD project, we wrote a simple model of mitochondrial calcium regulation based on an extensive review of models of the litterature, which are not suited for further calibration due to their excessive complexity [39]. Now that the equations are written down, we are performing a parameter analysis on the whole model before including other key biological mechanisms.

In a collaboration with Jeremy Darde (IMT Toulouse), we have developed a numerical method on a cartesian grid to solve the direct problem of Electrical Impedance Tomography (EIT) in complex geometries, with first-order convergence. The objective is to solve then the inverse problem of EIT to identify heterogeneities of conductivities on the torso volume.