The most common electrophysiologic mechanisms leading to SCD are tachyarrhythmias such as ventricular fibrillation (VF) or ventricular tachycardia (VT). Interruption of tachyarrhythmias, using either an automatic external defibrillator (AED) or an implantable cardioverter defibrillator (ICD), has been shown to be an effective treatment for VF and VT. The implantable defibrillator has become the central therapeutic factor in the prevention and treatment of sudden cardiac death.
Patients with tachyarrhythmias, especially VT, carry the best overall prognosis among patients with sudden cardiac arrest (SCA). Sudden unexpected cardiac death (SUCD) remains at a low rate at 0.4 - 2.4 per 100,000 person years until 30-35 years of age (50, 112, 113, 134, 135, 137, 143, 179) after which ischemic heart disease starts to take a heavier toll causing a significant rise in the incidence rate and eventually compromises 90% of SUCD cases.