Coronary artery bypass grafting (CABG), also known as bypass surgery, has been proven to be one of the most effective treatments for coronary heart disease after nearly 30 years of clinical practice. In recent years, there has been a rapid development in the treatment of coronary artery disease. Along with the development of technologies such as percutaneous transluminal coronary angioplasty (PTCA) also known as stenting surgery, CABG technology has also made great progress, especially the widespread application of arterial graft materials, the popularity of minimally invasive CABG, the increase in the success rate of surgery and the decrease in mortality, making CABG more competitive. Large domestic and international clinical studies have confirmed that CABG has a lower incidence of reoperation and better long-term results compared to PTCA. All this has led to a re-examination of the indications for the procedure. The clinical manifestations of coronary artery disease (CAD) are mainly angina pectoris. Due to the diversity of clinical manifestations of angina pectoris, the clinical typing of CAD is also varied, and the clinical typing of CAD is categorized as follows to facilitate clinical diagnosis and selection of surgical indications: I. Clinical typing 1. Asymptomatic or mild angina pectoris Patients have coronary artery stenosis, but they have not been feeling angina pectoris, or only during episodes of myocardial ischemia accompanied by chest discomfort. Sometimes myocardial ischemia is so severe that there is no pain even during an attack of myocardial infarction (MI). These asymptomatic myocardial ischemic events can be detected before serious cardiac events, such as abnormal ECG, arrhythmias, and positive angiographic findings. The poor prognosis of multiple episodes of asymptomatic myocardial ischemia on the dynamic ECG and the recent increase in episodes of ST-segment depression identify these CAD patients as being at increased risk for subsequent cardiac events. Early morning or nocturnal episodes of asymptomatic ST-segment changes are almost always associated with left coronary artery trunk stenosis and 2- or 3-branch coronary artery disease. Patients with ST-segment depression induced by exercise testing are expected to have 4-5 times higher cardiac mortality. 2. Chronic stable angina with typical angina symptoms that do not worsen significantly over several weeks. Typical symptoms occur with increased myocardial oxygen consumption and are quickly relieved by rest or nitrate medication. The ECG cannot confirm and exclude CAD because it is not uncommon for a resting ECG to show normal myocardial blood supply even when the coronary atherosclerotic lesion is severe. However, other manifestations of CAD can be detected. Exercise test ECG changes have a sensitivity of about 70% and a specificity of about 90% for the diagnosis of CAD. Compared to exercise testing, ambulatory ECG is difficult to provide additional important clinical information. Echocardiography allows accurate repeated measurements of cardiac size, ventricular wall thickness and left ventricular systolic and diastolic function, pulmonary artery pressure, and identification of complications such as ventricular wall aneurysms as well as appendicular thrombosis, mitral valve insufficiency, septal perforation, and calcified plaques in the ascending aorta and carotid arteries. In patients who cannot tolerate ECG exercise testing, dobutamine loading echocardiography can be used as a complementary method to observe the presence and location of myocardial ischemia during exercise. Radionuclide imaging has been a reliable noninvasive test for the diagnosis of coronary artery disease, the degree and extent of coronary artery lesions, myocardial viability, the estimation of therapeutic efficacy, and the prognosis. Coronary angiography is still the most reliable method for evaluating coronary artery lesions and is the main basis for drug therapy, interventional therapy and coronary artery bypass grafting (CABG) for coronary artery disease. Coronary artery enhancement CT can clearly show the degree and scope of coronary artery lesions, which is a more reliable, non-invasive and low-cost method to evaluate coronary artery lesions. Unstable angina (UA)/non-ST-segment elevation myocardial infarction (NSTEMI)/non-Q-wave myocardial infarction (NQMI) According to the Canadian Cardiovascular Society classification, unstable angina (UA) includes: 1, new onset angina: occurring in the last 1 month, with a tendency to worsen, degree 3 or more. 2, aggravated angina: previous angina attacks are frequent, prolonged, and increased in severity. 3. Resting angina: Angina attacks at rest and lasting for more than 20 minutes. UA can be manifested as ST-segment elevation on the ECG, or no elevation. Most people with ST-segment elevation eventually develop Q-wave myocardial infarction (QMI), and a few develop NQMI. people without segment elevation often develop NQMI, and very few develop QMI. UA/NSTEMI/NQMI and QMI are a group of clinical syndromes with similar etiology and clinical manifestations, but different severity – acute coronary syndromes. The main difference between the two is whether the ischemia is severe enough to detect the myocardial damage markers troponin I, T or CK-MB. When the marker concentration is normal, the diagnosis is UA, and when the marker concentration exceeds normal, the diagnosis is NSTEMZ or NQMI. 4, ST-segment elevation myocardial infarction/myocardial infarction with Q waves (STEMI/QMI) In the World Health Organization study on disease incidence, myocardial infarction (MI) is diagnosed with two of the following three characteristics: typical symptoms (angina lasting longer than 20 minutes) elevated myocardial marker concentrations and typical ECG manifestations of Q waves. MI is caused by prolonged myocardial ischemia, resulting in myocardial cell death and complete necrosis of the affected myocardium, which takes at least 4-6 hours; it also depends on whether the coronary artery is continuously blocked and on the collateral blood flow in the myocardial ischemic area. Infarcts are usually classified according to the size and location of the infarct and staged according to the pathological manifestations: acute (6h-7d), healed (8d-28d), and already healed (more than 29d). However, it should be emphasized that the pathological changes of the staging are not the same as the clinical manifestations in time: if the pathology has shown that the infarction is in the healing phase, the ECG may still show progressive S-T segment changes. Cardiac troponin remains increased. Echocardiography can clarify left ventricular function and the presence of mechanical complications of acute infarction such as left ventricular wall tumor, septal perforation, and mitral valve insufficiency. When determining the treatment method, it is necessary to consider which is the most effective, lowest risk and least expensive treatment method for the patient compared with drug therapy, PTCA and CABG. Coronary artery bypass grafting (CABG) is one of the most widely used surgical procedures at home and abroad with the best long-term outcome. Indications for the procedure: 1. Asymptomatic or mild angina (1) Severe stenosis of the left main trunk and similar left main trunk lesions (stenosis of the proximal diameter of the left anterior descending branch and the gyrus branch up to 70% or more) confirmed by coronary angiography, with the distal end of the stenosis open and greater than 1.5mm, is an absolute indication for the procedure. (2) Three branch lesions, especially combined with left heart insufficiency (EF value less than 50%), benefit more from CABG surgery than other means and are also very clear indications for surgery. (3) Single or two-branch lesions including severe stenosis of the proximal left anterior descending branch are favored for surgical treatment. (4) For single or two-branch lesions that do not involve the proximal left anterior descending branch, CABG is strongly recommended if other tests reveal a large cardiac emergency near death and low left heart function. In such patients, the aim of CABG is not to eliminate symptoms, but rather to extend life and improve survival as compared to non-surgical means of treatment. 2, chronic stable angina, the indications for surgery are the same as for asymptomatic or mild angina. As the symptoms are heavier than the former, CABG is also strongly recommended for single or two lesions with significant proximal stenosis of the left anterior descending branch if the left ventricular EF is less than 50%, or if other tests reveal the presence of myocardial ischemia. In such patients, the aim of CABG is to eliminate symptoms and prolong life. 3. Unstable angina (UA)/non-ST-segment elevation myocardial infarction (NSTEMI) The indications for surgery are the same as for asymptomatic or mild angina and chronic stable angina. However, the timing of surgery becomes a critical issue, as acute UA/NSTEMI/NQMI has a 2-3 times higher mortality rate than stable angina surgery, so it is emphasized to treat such patients with the maximum dose of medication they can tolerate and wait until their condition is stable and progressive ischemia resolves before performing CABG. If angina recurs despite the maximum dose of medication (approximately 33% of patients), CABG must be performed immediately. CABG must be performed immediately, and its long-term outcome is the same as that of stable angina, despite the high perioperative mortality. In such patients, CABG may clearly eliminate symptoms and prolong life. The later the surgery is performed after AMI, the lower the perioperative mortality rate. For progressive myocardial ischemia/infarction despite intensive nonoperative therapy (thrombolysis or PTCA), CABG may be attempted if there is still surviving myocardium and a suitable target vessel. Patients with cardiogenic shock or mechanical complications (e.g., septal perforation, papillary machine infarction/segmental inferior mitral valve closure insufficiency, left ventricular rupture) must be operated on urgently to resuscitate the patient. 5. For patients with obvious evidence of ischemia combined with LV insufficiency, fatal arrhythmias, PTCA failure or restenosis, or after previous CABG (obstruction of more than 1 vascular bridge, or atherosclerotic lesions dilated to other vessels), CABG should be actively performed if there is still surviving myocardium and suitable target vessels. III. Contraindications to surgery 1. Multi-organ failure, cardiac aspects The presence of severe chronic congestive heart failure combined with pulmonary hypertension, who cannot tolerate surgery. 2. No surviving myocardium and suitable target vessels.