Implantable cardioverter defibrillator (ICD) devices have been used for many years to prevent sudden cardiac death. Rapidly evolving ICD technology has widened the indications and clinical applications of these devices. Despite the technological advances, however, patients with ICDs are still at risk of sudden arrhythmic cardiac death. Furthermore, ventricular arrhythmias that require shock therapy, and inappropriate shocks triggered by supraventricular arrhythmias, adversely affect the quality of life of patients with implanted ICDs. However, many patients with ICDs have been discharged with no antiarrhythmic drug prescription. The addition of adjuvant antiarrhythmic drug treatment to ICD therapy is frequently required after the first shock therapy, to improve the quality of life of these patients.