KCND3 and atrial fibrillation: Although Kv4.3 and Kv4.2 mutations have been identified in AF patients, possible causality between these three identified genetic variants and AF has not been demonstrated, especially in respect of possible similarities or differences in their pro-arrhythmic effects, as the mutations occur in Kv4.3 (T361S and A545P) and Kv4.2 (S447R), two different proteins underlying the channels responsible for transient outward potassium current Ito [1].