I. Symptoms 1. Typical chest pain is triggered by physical activity, emotional excitement, etc. The pain is suddenly felt in the precordial region, mostly as episodic colic or crushing pain, but also as a feeling of suffocation. The pain starts from the posterior sternum or precordial area and radiates upward to the left shoulder, arm, and even the little finger and ring finger, which can be relieved by resting or taking nitroglycerin. The site of chest pain dispersion may also involve the neck, jaw, teeth, abdomen, etc. Chest pain can also appear in the quiet state or at night and is caused by coronary spasm, also known as variant angina pectoris. If the nature of chest pain changes, such as the newly emerged progressive chest pain, the pain threshold gradually decreases to the point that it can also occur during slight physical activity or emotional excitement or even at rest or when sleeping. The pain gradually increases, frequency, and duration is prolonged, and cannot be relieved by removing the trigger or taking nitroglycerin, then unstable angina is often suspected. When myocardial infarction occurs, the chest pain is severe and lasts for a long time (often more than half an hour), which cannot be relieved by nitroglycerin, and there may be nausea, vomiting, sweating, fever, and even cyanosis, blood pressure drop, shock, and heart failure. 2, need to pay attention to: some patients have atypical symptoms, only manifested as precordial discomfort, palpitations or weakness, or mainly gastrointestinal symptoms. Certain patients may not have pain, such as the elderly and diabetic patients. 3, sudden death: about 1/3 of patients with the first attack of coronary heart disease manifested as sudden death. 4, other: may be accompanied by systemic symptoms, such as fever, sweating, panic, nausea, vomiting, etc.. Patients with combined heart failure may appear II. Signs Patients with angina pectoris have no special when they do not have an attack. Patients may have diminished heart sounds and pericardial friction sounds. In case of ventricular septal perforation, murmurs can be heard in the corresponding area. In case of arrhythmia, the heart rhythm is irregular on auscultation. (1) Electrocardiogram Electrocardiogram is the easiest and most commonly used method to diagnose coronary artery disease. It is the most important test especially when the patient has an attack, and it can also detect arrhythmia. Most of them are non-specific when there is no attack. The S-T segment is abnormally depressed during an angina attack, and patients with variant angina present with transient S-T segment elevation. Unstable angina mostly has significant S-T segment depression and T-wave inversion. ECG manifestations in myocardial infarction: ① abnormal Q waves and S-T segment elevation in the acute phase; ② abnormal Q waves and T wave inversion only in the subacute phase (days to weeks after infarction); ③ abnormal Q waves only in the chronic or old phase (3 to 6 months). If S-T segment elevation persists for more than 6 months, there is a risk of complicating ventricular wall tumor. If the T wave is persistently inverted, it is called old myocardial infarction with coronary ischemia. (2) ECG loading test Including exercise loading test and drug loading test (such as pansentine, isoproterenol test, etc.). For patients who are asymptomatic in the quiet state or whose symptoms are very short and difficult to capture, myocardial ischemia can be induced by increasing the load on the heart through exercise or drugs, and the presence of myocardial ischemia can be confirmed by the change of ST-T recorded on the electrocardiogram. Exercise stress tests are most commonly used, and a positive result is considered abnormal. However, it is contraindicated in patients with suspected myocardial infarction. (3) Ambulatory ECG is a method that allows continuous recording and analysis of ECG changes in active and quiet states over a long period of time. This technique was first used by Holter in 1947 to monitor electrical activity, so it is also called Holter, and it can record changes in the ECG during daily life, such as ST-T changes due to transient myocardial ischemia. It is non-invasive, convenient, and easily accepted by patients. (4) Nuclear myocardial imaging can be performed when angina cannot be ruled out based on medical history and ECG examination, and when some patients cannot perform exercise stress test. Nuclear myocardial imaging can show the ischemic area and clarify the location and extent of ischemia. In combination with exercise stress test, the detection rate can be increased. (5) Echocardiography Echocardiography is one of the most commonly used tests for examining the morphology, structure, wall motion, and function of the left ventricle. It has important diagnostic value for ventricular wall tumors, intra-cardiac thrombus, heart rupture, and papillary muscle function. However, its accuracy is closely related to the experience of the ultrasonographer. (6) Hematological examination Usually requires blood collection to measure blood lipids, blood glucose and other indicators to assess the presence of risk factors for coronary heart disease. Myocardial injury markers are one of the important tools for the diagnosis and differential diagnosis of acute myocardial infarction. At present, cardiac troponin is mainly used in clinical practice. (7) Coronary CT Multilayer spiral CT cardiac and coronary imaging is a non-invasive, low-risk and rapid screening method, which has gradually become an important means of early screening and follow-up of coronary heart disease. It is suitable for: ① patients with atypical chest pain symptoms, where the diagnosis cannot be confirmed by auxiliary tests such as ECG, exercise stress test or nuclear myocardial perfusion; ② diagnosis of patients with low risk of coronary artery disease; ③ suspected coronary artery disease, but coronary angiography cannot be performed; ④ screening of asymptomatic patients with high risk of coronary artery disease; ⑤ follow-up after known coronary artery disease or interventional and surgical treatment. (8) Coronary angiography and intravascular imaging are the “gold standard” for the diagnosis of coronary artery disease, which can clarify the presence or absence of stenosis, the location, degree and extent of stenosis, and guide further treatment accordingly. Intravascular ultrasound can clarify the wall morphology and degree of stenosis in the coronary arteries. Optical coherence tomography (OCT) is a high-resolution tomographic imaging technique that allows better visualization of the vessel lumen and vessel wall changes. Left ventriculography allows for the evaluation of cardiac function. The main indications for coronary angiography are: ① for those who have severe angina despite medical treatment, to clarify the arterial lesion in order to consider bypass graft surgery; ② for those whose chest pain resembles angina but cannot be diagnosed.