KCNN4 and atrial fibrillation: Some calcium activated K+ channels, including small conductance (SK1, SK2, SK3) and intermediate conductance (SK4, also called KCa3.1) calcium-activated K+ channels, have been linked to arrhythmogenesis in atrial fibrillation (AF) and catecholaminergic polymorphic ventricular tachycardia (CPVT) [7,8].