Low ejection fraction, on the other hand, is an ejection fraction that is lower than the normal percentage. This is mainly due to abnormal enlargement of the ventricles and reduced ventricular function. Patients presenting with cardiac insufficiency often have a reduced ejection fraction. The chance of sudden death from malignant arrhythmias increases significantly when the ejection fraction drops below 35%. What can we do to prevent the occurrence of low ejection fraction? According to some international studies on ICD treatment: ICD treatment group reduces mortality by 28%, arrhythmia death by 50%, and heart failure ejection fraction low population (EF pulmonary edema and other heart failure patients heart failure warning signs), for the diagnosis and treatment of other cardiovascular diseases. Prevention of low ejection fraction should do five things. 1, is that the prevention knowledge should be widely spread in rural areas and communities to achieve the standardization of CPR education. When it comes to CPR, the first impression of the people should be to do cardiac compressions, rather than mouth-to-mouth artificial respiration. 2, gradually promote the popularity of external defibrillators (AED) placed in public places. 3.For patients with myocardial infarction and heart failure, use buried defibrillators (ICDs) prophylactically to prevent problems before they occur. 4.Preventive treatment for etiology and various variable risk factors, such as smoking cessation, alcohol, antihypertensive, lipid lowering and other treatments. 5, the mechanism of sudden cardiac death in the clinic is mainly ventricular fibrillation and other malignant ventricular arrhythmias, therefore, the prevention of sudden cardiac death, the key is the prevention of malignant ventricular arrhythmias, generally for primary prevention and secondary prevention, primary prevention refers to the risk of malignant ventricular arrhythmias in the occurrence of malignant ventricular arrhythmias, but there is no clinical malignant ventricular arrhythmias occurring in the population, should prevent the occurrence of malignant ventricular arrhythmias, such as no In patients with chronic congestive heart failure, β-blockers should be applied on the basis of adequate use of angiotensin-converting enzyme inhibitors (ACEI), digitalis and diuretics. Secondary prevention refers to the occurrence of clinically existing malignant ventricular arrhythmias without a clear cause (e.g., early acute myocardial infarction, low potassium, low magnesium, arrhythmogenic effects of antiarrhythmic drugs Secondary prevention is the first choice of ICD (buried cardioverter-defibrillator), and if ICD is not available, amiodarone or a combination of antiarrhythmic drugs should be used.