Chest pain is a very common clinical symptom, whether in respiratory medicine or cardiology, the vast majority of chest pain is caused by chest disease, with a few being due to other diseases. The degree of chest pain can be large or small and does not necessarily correspond to the location and severity of the lesion. Severe causes of chest pain can be critical if not detected and treated in a timely manner, such as acute heart attack. Therefore, in the face of a patient with chest pain, whether it is an emergency or on the night shift, it is very important to make correct judgment and appropriate treatment. The following four causes of chest pain must be ruled out first. Acute coronary syndrome (ACS) ACS is a group of clinical syndromes caused by acute myocardial ischemia, mainly including unstable angina (UA), non-ST-segment elevation myocardial infarction (NSTEMI) and ST elevation myocardial infarction (STEMI). In particular, myocardial infarction, if not recognized immediately and treated accordingly, can lead to major mistakes, lawsuits and regret. All patients with chest pain, especially those over middle-aged, must be excluded from having ACS beforehand, and routine electrocardiography is essential! Very necessary! Very necessary! It is important to say it three times. Diagnosis is based on medical history (presence of hypertension, coronary artery disease) and typical angina symptoms, typical ischemic ECG changes, and myocardial injury marker measurements. Dynamic monitoring of ECG and cardiac enzymes and myocardial injury markers. Do a good job of communicating the condition and informing the family that if it is ACS, it can be fatal and it is not a joke. Pulmonary thromboembolism is called pulmonary embolism when the thrombus in the veins of body circulation or right heart enters the pulmonary circulation and blocks the pulmonary artery or its branches. It often causes chest pain, the pain can be stabbing pain, colic, site in the back of the sternum, can radiate to the shoulder, intensify with breathing, at the same time there may be fever, dyspnea, hemoptysis (the so-called triad of signs is only seen in less than 20% of patients) and other symptoms, and even sudden death! Anyone with a history of prolonged bed rest, recent surgery, tumor, long-term oral contraceptives, etc., must exclude the possibility of pulmonary embolism once chest pain occurs! Arterial blood gas often shows hypoxemia, hypocapnia, etc. ECG is mostly non-specific abnormal. A normal chest radiograph does not exclude pulmonary embolism. In patients with high suspicion, CT pulmonary angiography must be performed to confirm the diagnosis if the situation allows. Aortic coarctation Pain is a common manifestation of aortic coarctation. About 90% of patients have sudden onset of severe, tearing or knife-like pain in the chest or thoracic back, which may radiate to the back of the shoulder, especially along the interscapular region to the chest, abdomen and lower extremities! Most patients have hypertension at the same time. Aortic coarctation is the opposite of the main treatment principle of acute heart attack, and once misdiagnosed, it is easy to get into lawsuits, so be careful! This is because patients with aortic coarctation may be very, very similar to an acute myocardial infarction, including electrocardiogram and myocardial enzyme changes. Once suspected, diagnosis must be made with ultrasound, CT, MRI and other diagnostic tools and treated quickly to reduce mortality. Pneumothorax Compared to the above diseases, the diagnosis of pneumothorax is relatively simple. Most patients with pneumothorax have an extremely sudden onset, with the patient suddenly feeling chest pain on one side, pinprick-like or knife-like, followed by chest tightness and dyspnea, and available irritating cough. In case of tension pneumothorax, rapid respiratory and circulatory disturbances can occur and must be diagnosed and treated as soon as possible. Most of the respiratory patients who present with pneumothorax are elderly patients with long-term chronic lung disease, so medical history is important. In massive pneumothorax, the trachea is displaced to the healthy side, the affected side of the chest is elevated, respiratory movements and tactile fibrillation are diminished, and breath sounds are diminished or absent. Standing posteroanterior radiographic chest examination is an important method to diagnose pneumothorax. Once suspected, it must be acted upon. Sometimes it may be too late for chest X-ray examination (such as tension pneumothorax), but when the initial diagnosis can be made based on the patient’s history, clinical manifestations and physical examination, the positive intrathoracic pressure should be relieved quickly to avoid serious complications, and the chest may be exhausted by immediate thoracentesis. Chest pain is very common, every patient seen, every patient with chest pain encountered on duty should first rule out critical diseases that can be immediately fatal, sometimes the exclusion does not necessarily require perfecting all the tests, the key is that we want to get, and then quickly determine through history, clinical manifestations, physical examination and existing tests.