RYR2 and catecholaminergic polymorphic ventricular tachycardia 1: As discussed, in Section 3.1, one of the many unknowns in RyR channel gating is how the four subunits of RyR2 work together and this may be a particularly important consideration in CPVT1 patients where the genotype is heterozygous and it might be expected that the resultant RyR2 tetramers will also be heterologous.