The voltage-gated potassium channel Kv1.5, which mediates the cardiac ultra-rapid delayed-rectifier (IKur) current in cells [1], is an attractive familial atrial fibrillation (AF) type 7 drug target, because it is selectively expressed in the atria but not in the ventricles of human cells [2]. The gene discussed is KCNA5; the disease is atrial fibrillation.