LVEF is an indicator of left ventricular systolic function, which is not affected by heart rate and can accurately and objectively reflect cardiac pump function. Therefore, it has been referred to as the “gold standard” for prognostic investigations of cardiac patients. When left ventricular function is reduced, it can cause increased compensatory sympathetic activity and suppressed vagal activity, which not only affects hemodynamics, but also increases the incidence of ventricular arrhythmias and the risk of sudden cardiac death. LVEF in normal subjects is 0.50-0.60, and it is generally believed that LVEF <0.4 is associated with increased post-infarction morbidity and mortality and has a definite predictive value for sudden cardiac death, and this predictive value is not easily influenced by drug therapy such as β-blockers. In contrast, other predictive methods such as QT dispersion and heart rate variability are susceptible to drug therapy such as β-blockers. a 10% increase in LVFF can reduce 2-year mortality. the rates of annual arrhythmic mortality in patients with LVFF values of 0.30-0.40, 0.21-0.30 and <0.20 were 3.2%, 7.7% and 9.4%, respectively. However, when LVFF is extremely low (<0.15-0.20), more slow arrhythmias than ventricular tachyarrhythmias occur, and the patient's death does not fall into the category of sudden death. 2, pressure reflex sensitivity (BKS) BKS reflects the rate of change of heart rate with changes in blood pressure, and is a sensitive indicator of changes in sympathetic and parasympathetic tone, which mainly reflects the reflex activity of parasympathetic nerves. Studies have shown a significant negative correlation between BRS and the incidence of ventricular fibrillation, and a significant increase in the incidence of malignant arrhythmias and sudden cardiac death in patients with reduced BRS. The literature reports a 50% mortality rate in patients with a significant reduction in BRS <3.Oms/mm Hg, compared with a 3% mortality rate in patients with BRS >3.Oms/mm Hg, and a positive predictive value of 50% for mortality with reduced BRS. 3, Ventricular late potential (VLP) VLP is the rupture potential generated by delayed depolarization of locally ischemic myocardium recorded by signal superimposed electrocardiogram (SAECG), which is closely related to persistent ventricular tachycardia in myocardial ischemia. Because of the abnormal electrical activity of ischemic myocardium, especially the slow electrical activity around the infarct, it is easy to cause folding excitation and malignant arrhythmia, so VLP can be used as the folding of ischemic area VLP can be a marker for the development of ventricular arrhythmias with ischemic zone folding mechanism. The sensitivity of VLP in predicting malignant arrhythmias was 92% and the specificity was 62%. The risk of sudden death was 5-10 times higher in VLP-positive patients with acute infarction than in negative patients, so VLP can be a valuable screening method for predicting fatal arrhythmias. elsherif studied the prognostic value of VLP present at different times after infarction and found that VLP detection rate was highest (25%) 6-30 days after myocardial infarction and was most associated with sudden death events within 1 year. Within one year of infarction, the incidence of sustained ventricular tachycardia in patients with abnormal SAECG was 14% to 29%, while the incidence of ventricular tachycardia in normal patients was only 0.8% to 4.5%. 4.Heart rate shock (HRT) HRT refers to the phenomenon of short-term heart rate fluctuation in the heart of patients with sinus rhythm after the occurrence of ventricular precontraction, including the three indicators of shock initial (TO), shock slope (TS) and shock dispersion (TD). In normal people and patients who are not prone to sudden death after infarction, their sinus heart first accelerates and then decelerates after the onset of ventricular premature contraction, and this condition is HRT. If HRT weakens or disappears after ventricular premature contraction, it is seen in patients at high risk of sudden death after infarction, and the electrocardiogram shows no significant change in the R to R interval of sinus rhythm before and after ventricular premature contraction. HRT reflects the bidirectional variable time function of the sinus node and suggests The state of autonomic function regulation is a non-invasive test to evaluate the autonomic regulation function of patients. The regulation function of autonomic nerve is closely related to cardiac arrest and sudden cardiac death, and if the parameters of heart rate oscillation are abnormal, it reflects the abnormal autonomic regulation function of the patient. Internationally renowned multicenter, large sample studies such as the MPIP, EMIAT and ATRAMI studies have shown that HRT in patients with acute myocardial infarction, heart failure and dilated cardiomyopathy are strongly and significantly correlated with total mortality and can be used as an independent predictor of death. TS is a strong predictor of risk in patients with heart failure. Currently, HRT is considered to be a high-risk predictor of death after myocardial infarction, and its evaluation is better than late ventricular potentials and heart rate variability, and is a strong independent predictor of death after myocardial infarction after cardiac ejection fraction (EF), and an evaluation indicator of prognosis of patients with myocardial infarction. If evaluated in combination with indicators such as left ventricular ejection fraction, it will increase the accuracy of prognosis of patients. What is most noteworthy is that the evaluation of prognosis by HRT is neither affected by the use of β-blockers nor by frequent ventricular anterior contractions, and it can be easily implemented in the routinely applied dynamic ECG analysis system, which is ideal for widespread promotion in hospitals at all levels. 5.Aspirin resistance test Aspirin can play a very important role in the prevention and treatment of cardiovascular events, but Eikelboom and other studies have demonstrated that some patients taking aspirin have aspirin resistance, or aspirin resistance phenomenon, so it suggests that these people belong to the high-risk group prone to cardiovascular events. In this population, aspirin failed to inhibit thromboxane production, as evidenced by elevated urinary concentrations of 11-dehydrothromboxane B2 (11-dhTB2). Among 5529 individuals who obtained baseline urine samples and followed the trial for 5 years, 488 aspirin-treated individuals experienced cardiovascular events, compared with 488 age- and sex-matched individuals who also used aspirin but had no cardiovascular events, and the risk of cardiovascular events was found to be 1.8 times higher in those with urinary H-dhTB2 concentrations in the upper quartile compared with those in the lower quartile, including a 2-fold higher risk of myocardial infarction and a 3.5-fold higher risk of cardiovascular In a prospective study of 326 stable cardiovascular patients taking 325 mg of oral aspirin daily, Gum et al. showed that the risk of cardiovascular events was three times higher in aspirin-resistant patients than in sensitive ones.