In this study, the impact of six mutations in KCNA5 on human atrial electrical function was investigated in silico, which elucidates and clarifies the arrhythmogenic effect of the six identified KCNA5 mutations, demonstrating a causal link between the mutations and incidence of arrhythmia—a link which is distinctly different for the two groups of mutations. This evidence concerns the gene KCNA5 and cardiac arrhythmia.