Ventricular fibrillation and sustained polymorphic ventricular tachycardia are malignant arrhythmias resulting in sudden cardiac death. Sudden cardiac death is a leading cause of death in the industrialized world, with Ventricular fibrillation and polymorphic ventricular tachycardia accounting for up to one-third of all cases. Though the majority of Ventricular fibrillation/polymorphic ventricular tachycardia occurs in structurally abnormal hearts, there is a subset of individuals resuscitated from sudden cardiac death with no structural heart disease. In some of these patients, Ventricular fibrillation/polymorphic ventricular tachycardia is triggered by premature ventricular complex that can be mapped and targeted by catheter ablation to prevent subsequent episodes. Patients with idiopathic Ventricular fibrillation are patients with prior history of resuscitated sudden cardiac death, but without structural heart disease or electrocardiographic abnormalities.