RYR2 and Arrhythmia: This inhibition of SERCA2A Ca2+ pumping by an excessive amount of Ca2+ to be pumped may explain previous observations of a slower rate and arrhythmia caused: (i) by catecholaminergic polymorphic ventricular tachycardia (CPVT) in which RyR mutations result in excessive RyR release [50] and also (ii) by “leaky” RyR, producing excessive Ca2+ release in the presence of ryanodine [51].