CALM3 and catecholaminergic polymorphic ventricular tachycardia: However, the recent research has led to the discovery of several CaM mutations in a small group of patients presented mainly with cardiac specific phenotypes, such as long QT syndrome (LQTS), idiopathic ventricular fibrillation (IVF), and catecholaminergic polymorphic ventricular tachycardia (CPVT).