Cardiac arrest is the sudden termination of cardiac ejection. The most common pathophysiological mechanisms leading to cardiac arrest are rapid ventricular arrhythmias (ventricular fibrillation and ventricular tachycardia), followed by slow arrhythmias or ventricular arrest and, less commonly, pulseless electrical activity (PEA). After cardiac arrest, due to the sudden interruption of cerebral blood flow, the patient can lose consciousness in about 10 seconds, and can survive with timely treatment, otherwise biological death will occur, and spontaneous reversal is rare. Sudden cardiac arrest is often the direct cause of sudden cardiac death. Sudden cardiac death (SCD) is a natural death of cardiac origin characterized by sudden loss of consciousness that occurs within 1 hour after the onset of acute symptoms. The timing and form of death is unpredictable, regardless of the presence of heart disease. The vast majority of sudden cardiac deaths occur in patients with organic heart disease. In Western countries, about 80% of sudden cardiac deaths are caused by coronary artery disease and its complications, and about 75% of these patients with coronary artery disease have a history of myocardial infarction. Decreased left ventricular ejection fraction after myocardial infarction is a major predictor of sudden cardiac death; the presence of frequent and complex ventricular asystole also predicts the risk of sudden death in survivors of myocardial infarction.