RYR2 and catecholaminergic polymorphic ventricular tachycardia: Although CPVT is well documented across CASQ2 and RYR2 variants, SAN dysfunction and atrial arrhythmias have been identified in CPVT patients, signifying the importance of calsequestrin-2 and ryanodine receptor 2 in proper SAN functioning (Sumitomo et al., 2007).