First, the complexity and diversity of the pathophysiological mechanisms and clinical manifestations of coronary heart disease coronary heart disease, also known as coronary atherosclerotic heart disease, refers to the atherosclerosis of the coronary arteries leading to narrowing of the lumen or blockage, thus causing myocardial ischemia or infarction of heart disease. Coronary heart disease is clinically divided into: ① chronic stable coronary heart disease, ② acute coronary syndrome (ACS). Chronic stable coronary heart disease: the pathophysiological mechanism is mainly due to the occurrence of severe atherosclerotic stenosis of coronary arteries leading to myocardial ischemia. The clinical manifestation is angina pectoris induced by a certain amount of exercise. Acute Coronary Syndrome (ACS): a clinical syndrome caused by acute stenosis or occlusion of coronary arteries. The pathophysiologic mechanism is very complex, mainly in the presence or absence of severe coronary artery stenosis or obstruction lesions, due to plaque rupture secondary to thrombosis caused by the blockage of blood vessels. In some patients, there is no serious stenosis of the coronary arteries, and there are no obvious symptoms before the onset of the disease, but ACS can be sudden, for example, nearly half of the patients with acute myocardial infarction have no history of coronary artery disease, but sudden. Clinical manifestations include: 1, cardiac death, 2, acute myocardial infarction, acute myocardial infarction, acute myocardial infarction is divided into ST-segment elevation acute myocardial infarction and non-ST-segment elevation acute myocardial infarction 2 categories, 3, unstable angina pectoris. The various manifestations of coronary heart disease depend on the complex pathophysiological changes of coronary heart disease, the latter and the coronary artery wall, lumen and intravascular blood properties and other abnormalities. Second, the early diagnostic strategy of coronary heart disease 1, according to the pathophysiological mechanism of coronary heart disease, the diagnostic strategy of coronary heart disease has the following 3 points: (1) Diagnose the myocardial ischemia or infarction (with or without coronary heart disease?). It mainly relies on the characteristics of symptoms during the attack and after remission, the characteristic changes of electrocardiogram and the abnormal elevation of cardiac biomarkers; if the opportunity of diagnosis during the attack is missed, it is necessary to diagnose the presence or absence of myocardial ischemia or myocardial infarction through a variety of examination methods, myocardial ischemia can be applied to cardiac loading (exercise, medication) test (electrocardiogram, echocardiogram and nuclear myocardial perfusion imaging), which can be induced in the state of cardiac loading and detect reversible myocardial ischemia, while myocardial infarction is diagnosed by electrocardiographic evolution and cardiac biochemical markers. (2) Identification of myocardial ischemia or myocardial infarction (which type of coronary artery disease?). It is very important for early diagnosis, mainly based on the clinical features at the time of the attack, the characteristic ECG changes and the abnormal elevation of cardiac biochemical markers, of which the clinical hold is the most important, the ECG changes are the corroborating evidence, and the cardiac biochemical markers are the final basis. (3) Definition of the coronary artery lesion causing myocardial ischemia or infarction (the nature and extent of the coronary artery lesion in this coronary artery disease patient?). This is the most direct anatomical evidence for the diagnosis of coronary artery disease, based primarily on the direct demonstration of noninvasive coronary computed tomography (CT), as well as the accurate diagnosis of invasive coronary angiography (still the gold standard). For chronic stable coronary artery disease, the key is to detect myocardial ischemia and severe coronary artery stenosis “as early as possible”; for ACS, the key is to diagnose myocardial ischemia or myocardial infarction “as soon as possible”, so as to facilitate emergency and standardized treatment. In particular, although ACS has precursor symptoms, but very mild, very easy to ignore and miss the diagnosis of coronary heart disease in the early diagnosis of the focus and difficulty. Evaluation of coronary heart disease diagnostic methods At present, the commonly used diagnostic methods for coronary heart disease include clinical symptoms, resting electrocardiogram, exercise electrocardiogram, load echocardiography, load isotope myocardial imaging, coronary CT angiography, coronary angiography and so on, of which coronary angiography is still recognized as the gold standard for the diagnosis of coronary heart disease. If these diagnostic methods are over-applied, it will result in a waste of medical resources, and if they are under-applied, they will not be able to diagnose accurately at an early stage, so how to reasonably and optimally apply them is a difficult point, and it is necessary to make a systematic evaluation of their diagnostic value. 2.1 Clinical symptoms and resting ECG Whether it is myocardial ischemia or myocardial infarction, the clinical manifestations of the characteristic episodes with the characteristic changes of ECG are the cornerstone and important basis for the diagnosis of coronary heart disease. Clinical symptoms, i.e., the site of chest pain or chest tightness episodes, the nature of the chest pain, the duration of the chest tightness, triggering factors and the mode of relief and other characteristic manifestations combined with the ECG characteristics of the changes, especially in the early diagnosis of ACS is more important. Electrocardiogram with ST segment changes during chest pain episodes and ST recovery after chest pain relief supports the diagnosis of myocardial ischemia angina pectoris; if it is the dynamic evolution of a typical myocardial infarction, the diagnosis of myocardial infarction can be established. However, resting electrocardiogram has limitations in diagnosing coronary artery disease during non-chest pain episodes; normal electrocardiogram during non-episodes cannot be excluded from coronary angina pectoris, and non-specific ST-T changes persist without evolution during non-myocardial ischemic episodes, so clinically one cannot easily conclude the diagnosis of myocardial ischemia solely on the basis of resting electrocardiogram. 2.2 Cardiac loading test Cardiac loading test refers to a series of examinations in which myocardial ischemia is induced in patients under exercise or drug loading, and is observed and recorded by electrocardiography, echocardiography or nuclear myocardial perfusion imaging. Load test can directly detect myocardial ischemia, and indirectly suggests that the blood supply area of the coronary artery has serious stenosis and lesions. Clinically, it is mainly used for routine screening of chronic stable coronary heart disease, with an accuracy of 70%~90%, and mainly includes exercise electrocardiography, stress echocardiography and stress nuclear myocardial perfusion imaging. Exercise ECG tests include plate or bicycle exercise tests. Patients under exercise load, observe the changes of ECG, detect whether myocardial ischemia is induced, so as to diagnose coronary heart disease, the diagnostic accuracy is about 70%. It has the advantage of being simple and easy to perform, and has been routinely used for coronary heart disease screening in clinical practice. However, the ECG exercise test has a certain false-positive and false-negative rate, and it is difficult to detect coronary artery stenosis of less than 70% at an early stage. Stress echocardiography is mainly used to diagnose coronary artery disease on the basis of ventricular wall motion abnormality when myocardial ischemia is induced under load, with a diagnostic accuracy of about 80%, but it is not as easy as exercise electrocardiography, and has not been routinely used in clinical practice. Load nuclide myocardial perfusion imaging is to diagnose coronary artery disease by detecting reversible myocardial perfusion defects under load, i.e. myocardial ischemia, with a diagnostic accuracy of 90%, clinically it is the most accurate non-invasive method to diagnose stable coronary artery disease, with internationally recognized diagnostic value, and the U.S. guideline explicitly recommends load nuclide myocardial perfusion imaging as a coronary artery angiography, especially as an interventional therapy. The U.S. guidelines clearly recommend load nuclide myocardial perfusion imaging as coronary angiography, especially interventional therapy ” gatekeeper “, more widely used abroad, drug load and exercise load myocardial perfusion imaging diagnosis of coronary artery disease sensitivity and specificity is not significantly different. However, its examination price is expensive, and isotope supply is inconvenient, radioactive, domestic application is more restricted, most of them are only routinely used in medical institutions above the provincial level. 2.3 Multi-slice CT (MSCT) MSCT coronary imaging can directly display the coronary artery lesion site, stenosis, and even the nature of the contrast agent, is the latest non-invasive imaging method for diagnosis of coronary artery stenosis and plaque, for the diameter of coronary artery segments ≥ 1.5mm, the diagnosis of coronary artery stenosis (＞ 50%) of the sensitivity of 83% ~ 93%, specificity of 82% ~ 97%, positive predictive value of 82% ~ 97%, positive prediction value of 50% ~ 97%, and the sensitivity of the diagnosis of coronary artery stenosis. ~97%, with a positive predictive value of 71%~83% and a negative predictive value of 92%~98%. The higher negative predictive value can help clinical exclusion of coronary artery stenosis and reduce the misdiagnosis rate. Through the CT values, MSCT is also able to determine the general tissue composition and nature of coronary plaque, thus enabling a preliminary assessment of the risk of plaque. In addition, MSCT coronary imaging is able to show the status of the lumen, the location of the stent pattern, and the bridge vessel after stent implantation or coronary artery bypass grafting, and can be used for postoperative follow-up.Although MSCT is a noninvasive and reliable technique for the early diagnosis of coronary artery disease at present, MSCT imaging is affected by heart rate, rhythm, coronary artery calcification, stenting, and pacemakers, and there are X-ray radiation safety issues, so it should be strictly checked and controlled. There is also the problem of safety of X-ray radiation, so the indications for examination should be strictly grasped, do not overdo the examination, and the clinic can not be used as a screening tool for the diagnosis of coronary heart disease. 2.4 Coronary angiography and related invasive techniques Coronary angiography is an invasive technique to visualize the coronary arteries by selective intracoronary injection of contrast medium, which can directly display the anatomy of the coronary arteries, as well as the location, stenosis and basic nature of coronary artery lesions, and it is still the most accurate examination method and the gold standard for diagnosis of coronary heart disease and other coronary artery diseases, and it can make a clear diagnosis and determine the treatment strategy; It can also evaluate and predict the long-term prognosis of patients. Nevertheless, due to the invasive nature of coronary angiography, there is a risk of possible complications, which should be strictly indicated and not abused. 2.5 Cardiac biochemical markers Clinically, they are mainly used to detect myocardial necrosis and ischemic injury in patients with ACS, and have a final confirmatory value in the diagnosis of myocardial infarction. Cardiac biochemical markers refer to proteins or cardiac enzymes that are released from necrotic myocardium into the bloodstream after myocardial injury or necrosis. Sensitive cardiac biochemical markers can detect small focal myocardial infarctions without ECG changes. It is recommended to be measured at the moment of admission, 2-4h, 6-9h and 12-24h. Troponin is the most sensitive and specific marker of choice for the diagnosis of myocardial necrosis. It begins to rise 2-4h after the onset of AMI symptoms, peaks at 10-24h, and disappears after 2 weeks. Troponin exceeding the upper limit of normal combined with evidence of myocardial ischemia can diagnose AMI. without the conditions to measure troponin, can be measured CK-MB instead. CK-MB usually starts to rise 6~8 hours after myocardial infarction, peaks at 12~24 hours (depending on whether the coronary artery is recanalized early or not), and disappears from the blood at 48~72 hours.CK-MB is also used in the diagnosis of recurrent myocardial infarction, and continuous measurement of CK-MB can also determine the opening of infarct-related arteries after thrombolytic therapy, in which case the peak value of CK-MB is shifted forward (within 14 hours). Because of the lack of specificity or poor specificity for the diagnosis of AMI, phosphocreatine kinase (CK), as well as as aspartate aminotransferase (AST), lactate dehydrogenase (LDH), and lactate dehydrogenase isoenzymes are no longer recommended for the diagnosis of AMI. Myoglobin measurement helps in early diagnosis but has poor specificity. Especially important is that, although the cardiac biochemical markers are the final basis for the final diagnosis of AMI, but in the diagnosis of ST-segment elevation acute myocardial infarction, must not wait for the elevation of markers to confirm the diagnosis and delay coronary artery reestablishment therapy, including emergency PCI or thrombolytic therapy, should be based on the symptoms and electrocardiograms as soon as possible to make a diagnosis as soon as possible to carry out the reestablishment of blood flow as soon as possible. Early diagnosis of coronary heart disease Whether it is stable coronary heart disease or ACS, the basic strategy for early diagnosis of coronary heart disease is: early diagnosis of myocardial ischemia or infarction; early diagnosis of ischemia or infarction-related lesions. The basic diagnostic ideas are as follows: 3.1 Stable coronary heart disease According to the medical history, clinical symptoms and ECG changes, if the diagnosis can be initially confirmed, it can be directly recommended to coronary artery angiography and related coronary artery blood flow reconstruction treatment. If the diagnosis cannot be confirmed, cardiac stress test (electrocardiogram and/or isotope examination) and/or MSCT coronary artery imaging (CTA) are feasible. For those with positive stress test or severe coronary artery stenosis shown by CTA, coronary angiography and related coronary artery revascularization therapy are recommended; for those who cannot be diagnosed conclusively, systematic examination should be carried out to determine or to exclude the existence of other cardiovascular diseases, which may also be recommended. Coronary angiography should be performed to confirm or exclude coronary artery disease. 3.2 ACS According to the onset of chest pain in clinical symptoms and ECG changes, for ST-segment elevation acute myocardial infarction that can be diagnosed, coronary artery revascularization treatment should be carried out as soon as possible, including thrombolysis or emergency PCI; for non-ST-segment elevation acute myocardial infarction or unstable angina pectoris that can be diagnosed, risk stratification and corresponding treatment should be given. For suspected and undiagnosed patients, continuous observation (including symptoms and electrocardiographic changes) for another 6 to 12 hours and measurement of cardiac biochemical markers will be performed, and appropriate treatment will be given if the diagnosis can be confirmed. For those who can exclude ACS, further examination is recommended to determine or exclude the presence of coronary heart disease or other cardiovascular diseases. In conclusion, the early diagnosis of coronary heart disease depends on a number of clinical indicators clinical, especially for ACS must be diagnosed accurately as soon as possible, can not be delayed due to missed diagnosis of treatment, and stable coronary heart disease should also be diagnosed at an early stage, to choose the appropriate treatment program to prevent the occurrence of ACS.