A new model of the human atrial myocyte with variable T-tubule organization for the study of atrial fibrillation

Atrial fibrillation is the most common arrhythmia, yet treatment strategies are sub-optimal due to incomplete understanding of the underlying mechanisms. Spatio-temporal sub-cellular calcium cycling may play a critical role in the development of alternans and spontaneous activity, which may underlie arrhythmia in the human atria. In this study, we construct a novel electrophysiological model of the human atrial myocyte which incorporates new data on atrial intracellular structure and explicitly accounts for variations in T-tubule organization. The model reproduces spatio-temporal calcium dynamics associated with normal cardiac excitation. In preliminary simulations, the model demonstrates that a loss of T-tubules can promote both alternans and spontaneous calcium waves. The model produced in this study provides novel insight into arrhythmia mechanisms in the human atria and provides a platform for future investigation of pro-arrhythmic calcium dynamics.