RYR2 and catecholaminergic polymorphic ventricular tachycardia: Secondly, the higher frequency and amplitude of sparks and whole-cell SCW in CPVT CMs compared with controls is consistent with a previous study that reported accelerated Ca2+ release restitution in CPVT CMs attributed to abbreviated RyR2 refractoriness (Brunello et al., 2013).