Global KO of Casq2 caused a full-blown CPVT phenotype characterized by premature ventricular contractions (PVCs) and bidirectional and polymorphic VT (Figure 1, D–F), comparable to what we have previously observed in a germline whole-heart Casq2–/– model (7). Here, CASQ2 is linked to catecholaminergic polymorphic ventricular tachycardia.