Mutations in the cardiac ryanodine receptor (RyR2), the ligand-gated SR Ca2+ release channel, can increase channel open probability during diastole, resulting in excess diastolic SR Ca2+ release, and lead to catecholaminergic polymorphic ventricular tachycardia (CPVT) (Laitinen et al., 2001; Lehnart et al., 2004; Priori et al., 2001; Swan et al., 1999), ventricular fibrillation (VF) (Cerrone et al., 2005; Jiang et al., 2007; Paech et al., 2014) or atrial fibrillation (AF) (Pizzale et al., 2008; Sumitomo et al., 2007). The gene discussed is RYR2; the disease is atrial fibrillation.