In simulations, we investigated the functional impact of the three Ito-associated gene mutations on human atrial electrical excitations and their conductions at the single-cell, tissue, and whole-organ levels in order to elucidate the mechanism(s) underlying the pro-arrhythmic effects of Kv4.2 and Kv4.3 mutations in AF. This evidence concerns the gene KCND3 and atrial fibrillation.