CASQ2 and catecholaminergic polymorphic ventricular tachycardia: Most mutations that have been linked to CPVT are found in two genes, ryanodine receptor 2 (RyR2; 50–55%) and calsequestrin 2 (CASQ2; 3–5%), two proteins fundamentally involved in regulation of intracellular Ca2+ in cardiac myocytes3,4.