RYR2 and catecholaminergic polymorphic ventricular tachycardia: However, the rate of sodium channel mutation (SCN5A) mutation is low in Asian patients with BrS31,32 and the rate of background mutations in ryanodine receptor 2 gene (RYR2) or calsequestrin 2 gene (CASQ2) are substantially high33, which sometimes make the definite diagnosis of BrS and CPVT even more difficult.