CASQ2 and catecholaminergic polymorphic ventricular tachycardia: Finally, ultrastructural analysis of CPVT2 cardiomyocytes showed a small expansion of the SR cisternae,37 as previously reported in a mouse model of CPVT with a deficient cardiac CASQ2.27,43,48 This expansion was suggested to constitute a compensatory response for the loss of SR Ca2+ buffering by the mutated CASQ2.27