Acute chest pain is a common presenting symptom in the emergency department and often requires diagnosis and differential diagnosis due to the involvement of cardiovascular, respiratory, gastrointestinal, musculoskeletal, and neurologic disorders. Fatal chest pain, including acute coronary syndrome (ACS), pulmonary embolism, aortic coarctation, pericardial tamponade, tension pneumothorax, etc., is the focus of clinical attention. History 1. ACS episodes of chest tightness, pressure or suffocation, discharging to the upper limbs, back or neck, induced by exertion and emotional stress, lasting minutes to tens of minutes, relieved by rest or nitroglycerin. ACS should be highly suspected, especially in patients with previous hypertension, diabetes mellitus, hyperlipidemia, smoking, family history of coronary heart disease. If the duration is more than 20min without relief, the possibility of myocardial infarction should be considered. 2.Pulmonary embolism. Chest pain with shortness of breath or hemoptysis after activity, relieved after rest, need to consider the possibility of pulmonary embolism. Especially patients with long distance flight history, lower extremity phlebitis, fracture, bed-ridden, taking contraceptives history. 3, aortic coarctation and large vessel disease persistent severe tearing chest pain, accompanied by back pain, blood pressure increased significantly, consider the possibility of aortic coarctation or other large vessel disease. Especially patients with a family history of large vessel disease. Physical examination The identification of large-vessel disease and pulmonary embolism, pericardial tamponade, pneumothorax, etc. should be made mainly through the blood pressure value and the symmetry of the blood pressure of the extremities, the presence of cardiac murmur, whether the second tone of the pulmonary artery is hypertonic, whether the respiratory sound of both lungs is symmetrical, whether there is any abnormal vascular murmur of the chest and abdomen, whether there is any asymmetry of the circumference of the lower limbs, and whether there is any phlebitis or edema. Auxiliary examination 1, electrocardiography. Typical ST-segment elevation or depression on ECG can be easily recognized. However, it should be noted that ECG changes must be interpreted in conjunction with the medical history, avoiding “picture by picture”. ST-segment elevation on the electrocardiogram can be seen in patients with typical acute myocardial infarction, but also in rare cases such as acute myocarditis, acute pulmonary embolism, and aortic coarctation. Myocarditis causes ST-T changes in a wide range of leads, mostly in the form of downward elevation or depression of the concave surface of the ST-T. A few cases of myocarditis may present changes similar to typical ST-segment elevation myocardial infarction-like changes and their evolution, the mechanism of which is unknown. Therefore, the differentiation of the above diseases should not only focus on the ECG changes, but also take into account the medical history, risk factors and other auxiliary tests. If the electrocardiogram is normal at the time of presentation, it should be repeated 6 h after admission or 6-12 h after chest pain. If the chest pain persists or needs to be relieved by nitroglycerin, the ECG should be reviewed as soon as possible. Echocardiography. Segmental dyskinesia is helpful in the diagnosis of ischemic heart disease. Widening of the root of the ascending aorta and intima-media flaky shadow are helpful in the diagnosis of macrovascular disease. Increased right heart load and pulmonary hypertension help in the diagnosis of pulmonary embolism. 3. Chest radiography. Chest radiography helps to exclude chest pain caused by lung diseases. In addition, widening of the mediastinum, bulging of the pulmonary artery segments, and thinning of the pulmonary vascular shadows are helpful in the diagnosis of large-vessel disease and pulmonary embolism. 4.Troponin, D-dimer, blood gas test. Troponin test has become necessary for the diagnosis of myocardial infarction. For those who have normal troponin at the time of diagnosis, it is necessary to repeat the observation of troponin changes in 6 h or 6~12 h after chest pain. Elevated troponin does not necessarily mean that myocardial infarction has occurred. Myocardial necrosis caused by vascular causes is called myocardial infarction, and myocardial necrosis caused by non-vascular causes is called myocardial injury. Troponin elevation due to acute myocardial infarction is characterized by short-term ups and downs. The rise and fall of troponin elevation due to other causes is atypical. Aortic dissection, pulmonary embolism, heart failure, myocarditis, hypertrophic cardiomyopathy, renal insufficiency, tachyarrhythmia and bradyarrhythmia can all lead to elevated troponin, which needs to be differentiated from myocardial infarction. Elevated D-dimer mainly indicates the activation of coagulation and fibrinolytic system in the body, pulmonary embolism, aortic coarctation, ACS can lead to the elevation of D-dimer, in addition, inflammation, tumors, etc. Negative D-dimer has a high diagnostic value, and a negative test can help to exclude acute pulmonary embolism. Blood gas test is helpful for the diagnosis of pulmonary embolism. 5.CT examination. For patients with high suspicion of macrovascular disease and pulmonary embolism, macrovascular CT and pulmonary vascular CT should be performed. Coronary CT angiography (CTA) Coronary CTA has high sensitivity (91%~99%) and specificity (74%~96%) for the diagnosis of coronary lumen stenosis, with an average negative predictive value of 97%. Due to its high negative exclusion diagnostic value for coronary heart disease, it has been gradually introduced into the early diagnosis of patients with suspected ACS, in addition to screening for suspected coronary heart disease. It is especially used for people with low risk of coronary heart disease or cardiovascular events. Some studies have shown that the application of CTA as a screening tool for ACS has a better price/efficiency ratio than the noninvasive cardiac stress test. With the development of new CT imaging technologies, the substantial increase in rack rotation speed and detector helical scanning coverage width is expected to be a useful tool for one-stop screening of the emergency chest pain triad (ACS, aortic coarctation, and pulmonary embolism).