Atrial fibrillation is the most commonly encountered clinical arrhythmia. Despite recent advances in treatment by catheter ablation, its origin is still incompletely understood and it may be difficult to treat. Computer modelling offers an attractive complement to experiment. Simulations of fibrillation, however, are computationally demanding since the phenomenon requires long periods of observation. Because the atria are thin walled structures, they are often modelled as surfaces. However, this may not always be appropriate because abrupt changes of fibre direction are encountered through the atrial wall, that have been observed to affect the electrical phenomenon.
I will present a bilayer model obtained by asymptotic analysis that remains computationally simple while retaining the main 3D features of the atrial wall. Afterwards, I will describe the semi-automatic procedure used to construct actual bilayer atrial models from medical images. Finally, I will show some numerical illustrations, such as a complex atrial arrhythmia developing over several heart beats, proving the medical relevance of the model.