To examine the anatomic origin of ventricular ectopy in CPVT, hearts were isolated from Casq2–/– mice and perfused in Langendorff mode with oxygenated Tyrode’s solution and the transmembrane potential dye di-4-aminonaphthylethenylpyridinium (ANEPPS). This evidence concerns the gene CASQ2 and catecholaminergic polymorphic ventricular tachycardia.