A portable electronic device intended for use at home to automatically detect cardiac arrhythmias (ventricular fibrillation/pulseless ventricular tachycardia) in a sudden cardiac arrest (SCA) patient, after which it audibly/visually instructs an operator to enable it to activate defibrillation of the heart through application of electrical shocks to the chest surface. It is designed to be used by a layperson and consists of an external pulse generator (EPG) and skin-adhesive electrodes that monitor the rhythm/deliver the shocks; it includes a non-rechargeable battery for energy that requires replacement when indicated by the EPG. It may be available [non-prescription] over-the-counter (OTC).