IK and atrial fibrillation: Although IK,ACh as well as IKur has been shown to be predominantly expressed in the atrium (Gaborit et al., 2007), IK,ACh and IKur inhibitors have been clinically shown to have a limited efficacy against AF (Heijman et al., 2017; Camm et al., 2019; Peyronnet and Ravens, 2019), implying the limitation of selective atrial ionic channel inhibitors.