1.Coronary artery bypass grafting: (CABG) professionally known as coronary artery bypass grafting, the procedure is to take a normal blood vessel from the patient, connect one end to the ascending aorta and the other end to the distal side of the coronary artery stenosis, because this surgical method is like a bridge, so the image is called coronary artery bypass grafting. The arterial blood in the aorta bypasses the original stenotic section of the coronary artery and reaches the distal coronary artery directly through the “bridge vessel”, so that the coronary blood flow in the distal part of the stenosis is restored to normal. 2.The purpose of coronary artery bypass surgery is to improve the blood supply to the heart through surgical methods. Due to the increased blood demand of the heart during exercise, the already narrowed coronary vessels cannot provide the necessary blood volume and angina and myocardial ischemia occur. After undergoing bypass surgery the blood supply to the heart is increased, directly resolving the contradiction between the supply and demand of the myocardium, so that the blood volume of the heart increases during exercise and myocardial ischemia no longer occurs, achieving relief of angina symptoms, resulting in a longer life expectancy and a reduced rate of sudden death in patients with coronary heart disease. Patients with long-term coronary artery stenosis inevitably develop ischemic cardiomyopathy, which causes the contraction capacity of the heart to decrease significantly and manifest as a hypocontractile state. Due to the timely improvement of the blood supply to the myocardium, bypass surgery allows the function of the ventricles to be protected. The benefit of surgical treatment also lies in restoring the patient’s quality of life, being able to fully enjoy life and restore the ability to work, as well as making the retirement life of elderly patients vibrant. 3, the indications for coronary artery bypass surgery: there are certain surgical indications for receiving bypass surgery, when the condition develops to the point where bypass surgery treatment is needed, surgery should be performed as early as possible, it is best to avoid myocardial infarction, because once myocardial infarction occurs, local myocardial necrosis occurs, the loss of myocardial contractile function, in such an area not only has lost the meaning of bypass, and any other treatment can not achieve results. Secondly, avoid prolonged preoperative myocardial ischemia, prolonged myocardial ischemia and angina attack make the local myocardium not get enough oxygen and nutrients, even if myocardial infarction does not occur, the cellular viability and contractile function of this part of the myocardium will be reduced, and serious ischemic cardiomyopathy can develop. The main principle of bypass surgery is to improve myocardial ischemia to the greatest extent possible and to reduce the risk to the patient. The lesion should be taken into account when selecting the treatment. The main indications for coronary artery bypass surgery are: (1) left main stem lesion with stenosis greater than 50%. (2) Significant stenosis (≥70% or more) in the proximal segment of the left anterior descending branch and the proximal segment of the left circumflex branch should be selected for bypass surgery. (3) Two or more vascular lesions in combination with diabetes, especially two vascular lesions with stenosis of the proximal segment of the anterior descending branch. (4) Diffuse lesions of three or more vessels with hypoplastic left heart should undergo bypass surgery. (5) Single-vessel lesions, especially long segment lesions of the anterior descending branch or the proximal segment of the right coronary artery. (6) Acute myocardial infarction with cardiogenic shock. (7) Combination of cardiac mechanical complications requiring surgical treatment such as tendon rupture mitral regurgitation, ventricular septal perforation or combined ventricular wall tumors. (8) Stable angina with ineffective medical treatment, unstable angina; post-infarction angina; myocardial infarction without Q waves. (9) Those who have failed partial intervention or have acute complications of rib, such as severe coronary injury. (10) Recurrence of angina pectoris after bypass surgery and bypass surgery again. In short: the basic indications for bypass surgery are patients whose symptoms of myocardial ischemia are not controlled by medical treatment, and generally speaking, the greater the extent of ischemia and the more severe the stenosis, the better the bypass effect. 4, contraindications: If the coronary artery lesion is diffuse distal coronary artery can not bypass surgery, serious cardiac, cerebral, pulmonary, hepatic and renal insufficiency can not tolerate surgical trauma blow is a contraindication to surgery. 5, the type of bypass surgery: the traditional bypass surgery requires the use of extracorporeal circulation in the state of cardiac arrest to complete the bypass surgery. The goal is for the surgeon to obtain a bloodless and quiet surgical condition to complete an accurate anastomosis on the heart vessels, but the use of extracorporeal circulation is inherently dangerous and may increase the risk of surgery. Surgical deaths and postoperative complications are mainly related to extracorporeal circulation, in addition to the complexity of the anesthesia and surgical procedure and the high use of disposable supplies. In the last decade, with medical development and technological advances, bypass surgery has been carried out by a method that does not stop the heart and does not require extracorporeal circulation, i.e. non-external circulation heart beating under bypass surgery (OPCAB). It is also the result of a perfect combination of continuous improvements in cardiac stabilization devices and cardiac surgery. It allows the small part of the heart that needs to be bypassed to remain in minimal motion while the vast majority of the heart is beating normally and working continuously to supply blood to the whole body, reducing myocardial reperfusion injury, successfully reducing surgical complications and promoting early recovery. The non-extracorporeal beating heart bypass surgery broadens the indications for coronary artery bypass surgery. For high-risk patients, especially those with pulmonary, renal, neurological and severe left heart insufficiency are more suitable for non-extracorporeal beating heart bypass. It simplifies an otherwise complex procedure, but requires more skill from the anesthesia and surgeon. This approach allows for a smoother and smoother recovery process after surgery. Fewer positive inotropic drugs are used, earlier weaning from the ventilator, shorter ICU ward and hospital stay reducing the possibility of secondary open heart hemostasis. Less surgical blood transfusion. Reduced incidence of postoperative vital organ failure. Reduced neurological, renal and pulmonary complications, eliminated many complications related to cardiac arrest and extracorporeal circulation, and reduced treatment costs. 6.Common bypass sites: (1) right coronary artery: right coronary artery trunk, anterior bifurcation, posterior descending branch, posterior left ventricular branch (2) anterior descending branch system: middle 1/3 of anterior descending branch, first or (and) second diagonal branch, intermediate branch (3) gyrus branch system: first or (and) second gyrus branch, posterior descending branch. 7. Vascular grafts for bypass surgery: (1) The commonly used graft arterial vascular bridges are the internal thoracic artery (ITA) (or internal mammary artery, IMA), radial artery (RA), right gastric omental artery (GEA), inferior abdominal artery (IEA), splenic artery, etc. The greatest advantage of using arterial vascular as bypass material is the high long-term patency rate, and the vascular patency rate is still about 90% ten years after surgery. (2) The commonly used graft vein bridge is the saphenous vein (LSV) of the lower extremity, with the calf portion of the saphenous vein preferred, followed by the thigh portion. If the saphenous vein is too large or severely varicose, it should be discarded, otherwise it is prone to vortex flow and easy to form thrombosis, and then the small saphenous vein or the precious meridians of the upper limb can be used. The advantages of using a vein as a bypass material are easy to take, rapid surgery, large internal diameter of the vein, easy anastomosis, low surgical mortality, smooth blood flow, and good recent surgical results. However, the vein wall, which was originally subjected to low pressure, has to be subjected to arterial pressure for a long time when it acts as the graft bridge in bypass surgery. The vessel wall is prone to degeneration, intimal hyperplasia, atherosclerosis, narrowing of the vessel diameter, and poor long term patency rate. If a patient needs to bypass a large number of vascular bridges, a combination of arterial and venous bridges should be used. The left internal mammary artery is routinely used to anastomose with the anterior descending branch, and the saphenous vein is anastomosed with the right coronary and gyral branches. 8.Risk factors of bypass surgery: The risk factors affecting the prognosis of coronary artery bypass surgery mainly depend on two aspects: on the one hand, the patient’s general health condition and the functional condition of the major organs of the body; on the other hand, the complete degree of surgical recanalization. The risk factors in the early postoperative period are mainly cardiac per se factors, such as history of previous cardiac surgery, angina pectoris grade III-IV, previous history of myocardial infarction, acute surgery and left ventricular functional status. In contrast, non-cardiac factors have a greater impact in the mid- to long-term postoperative period, including chronic obstructive pulmonary disease, renal failure, and severely impaired preoperative left heart function.