Coronary atherosclerotic heart disease (CHD) is one of the most common diseases affecting the health of modern people. Although it has been better understood in terms of etiology and pathology, and there has been great progress in treatment, acute myocardial infarction (AMI), one of the most serious conditions of coronary heart disease, still poses a serious threat to people’s health. It has been reported that about one and a half million people in the United States suffer from myocardial infarction each year, more than half of whom require hospitalization, and the most dangerous period is within the first h after an MI occurs, with about 1/6 people dying during this period (1)(2). The vast majority of patients after AMI can be treated with thrombolysis and PTCA to restore coronary blood flow, but some patients are not suitable for conservative treatment or cannulation intervention, some patients fail to undergo PTCA or develop complications, and others require coronary artery bypass grafting (CABG) due to complications of MI such as mitral valve insufficiency, ventricular septal defects, and ventricular wall aneurysms. These patients usually have an acute onset of illness and are often unstable, requiring surgery to be performed as soon as possible. Therefore, CABG surgery for these patients has a certain degree of urgency in time, and it is not appropriate to wait for the so-called emergency CABG surgery, which has gradually become an important part of cardiac surgery in Europe and the United States. It has gradually become an important part of cardiac surgery in Europe and the United States. Although it has just begun in our country, it is bound to increase in the future. (A), the mechanism of emergency CABG coronary artery blood flow obstruction less than 20min, myocardial cell damage and functional inhibition is reversible, followed by myocardial depression. After 40 min of flow obstruction, 60% to 70% of the myocardium can still recover. If the duration of obstruction exceeds 3 h, only 10% of the affected myocardium recovers (3). In addition, animal experiments and many clinical studies have demonstrated that ischemia lasting longer than 6 h can produce extensive transmural necrosis. Restoration of blood flow within 6 h reduces infarct size and improves survival (4). In patients with myocardial infarction lasting more than 6 h, it is unlikely that the size of the infarct zone will change after restoration of perfusion, but aggressive treatment may still help to improve the blood supply to tissues at the margins of the infarct, which is most likely to be reduced in the first few days after infarction. It can be seen that the period from the onset of symptoms to the restoration of blood flow is a very critical moment in the rescue of MI patients, and all possible means must be utilized to race against time to restore the blood supply to the infarcted area as soon as possible. (II) Characteristics of emergency CABG patients Among the patients who need to undergo emergency CABG, there are many older patients and many women, most of whom have left main stenosis or triple-branch vasculopathy, often accompanied by severe angina pectoris, peripheral vasculopathy and impaired left heart function. Some patients had experienced PTCA or CABG, were not currently suitable for conservative treatment, and most had hemodynamic instability present. Therefore, patients requiring emergency CABG are high-risk patients. (C) Indications for performing emergency CABG CABG becomes necessary when the outcome of emergency CABG is expected to be better than conservative treatment, thrombolytic therapy, or PTCA. The indications are as follows (5): 1. severe left main stenosis 2. 3-branch vasculopathy 3. impaired left heart function 4. unsuccessful thrombolytic therapy or contraindication to thrombolytic therapy 5. coronary anatomy unsuitable for or unsuccessful PTCA 6. severe unstable angina ineffective pharmacological treatment 7. recurrent MI 8. post-infarction angina 9. cardiogenic shock due to coronary ischemia (d), the definition of cardiogenic shock In the absence of blood volume reduction, systolic blood pressure is lower than 80 mmHg, peripheral vasoconstriction, cold extremities, altered state of consciousness, urine output less than 20 ml/L, cardiac index <1.8 liters/min/M2, volumetric index per blog <20 ml/M2, mean pulmonary capillary inlet pressure >18 mmHg, rapid heart rate, systemic vascular resistance >2400 dyn/cm5, can be diagnosed as cardiogenic shock (6). The presence of cardiogenic shock suggests myocardial involvement of at least 40% of the left ventricle and most often a triple-branching ductal lesion. The morbidity and mortality rate with cardiogenic shock can be as high as 80%, while cardiogenic shock can occur in 2.4% to 12.0% of patients with acute MI. The key to treatment is early restoration of myocardial blood supply. The use of mechanical circulatory support to rest the depressed myocardium for later recovery is also important. (E) Preoperative treatment 1. Monitor the patient closely in the ICU, and observe the hemodynamic changes closely with the possible monitoring means. At the same time, the cause of myocardial ischemia and the range of myocardial involvement should be determined as soon as possible to stabilize the hemodynamics of the patient. 2. In the application of drugs, sedation and oxygen can be given to relieve anxiety. Nitroglycerin can be given intravenously, and morphine, β-blockers or calcium blockers can be given. (3) IABP can be used to reduce the left ventricular systolic pressure and oxygen consumption, and at the same time increase the diastolic pressure to increase the blood supply to the ischemic area when the drug treatment can not maintain the circulatory stability. Risk factors related to surgery (7) 1. LVEF 2. number of involved coronary arteries 3. preoperative MI 4. hypertension 5. need for vasoactive drugs 6. need for IABP support 7. after cardiopulmonary resuscitation. Multifactorial analysis suggested that MI, post cardiopulmonary resuscitation, hypertension and reoperation were separate risk factors. (vii) Surgical techniques 1. Preoperative preparation Because the patient to be operated on is at high risk, the arterial sheath tube after catheterization should not be removed for insertion of an IABP if necessary. percutaneous perforation cardiopulmonary support may also be applied if hemodynamics are unstable, if an ischemic zone is evolving, or if surgery may be delayed because formal extracorporeal circulation (CPB) may not be established right away. A tracheal tube may also be inserted at the catheterization site in hemodynamically unstable patients. The choice of arterial and venous bridges and the establishment of CPB If the hemodynamics is still stable, the internal mammary artery can be routinely taken, and then CPB can be established; if the hemodynamics is unstable, only the saphenous vein can be used, and the CPB can be established immediately after the chest is opened.Usually the ascending aorta and the vena cava are still used to intubate, and in a small number of cases, the pulmonary artery is used for venous return intubation. In the case of re-CABG and hemodynamic instability, CPB can be established via femoral artery cannulation. 3. Intraoperative myocardial protection In the case of preoperative IABP, 60 beats/min counterpulsation can still be used in CPB. When the heart is in a state of emptying (no work), if there is still ST-T change, it should be cooled down to 28℃. Shun infusion of 700-1000 ml with crystalloid stopping fluid and continuous intraoperative cooling with ice saline maintains myocardial temperature at 5-10°C. Warm blood stopping can avoid the metabolic disorder caused by hypothermia and help myocardial function to recover quickly. However, it is more difficult to stop the beating, poorly revealed when performing distal anastomosis, and increases the risk of central nerve injury, so it is not routinely used much. Reverse irrigation is routinely used in some units, but the distribution of the stopping fluid is not uniform during reverse irrigation, and the continuous warm blood stopping applied at the same time increases the complexity of the operation, which is no longer used in most units. If the internal mammary artery is found to be small and postoperative cardiac abnormalities are anticipated, a venous bridge may be added. The distal anastomosis is usually performed first, and a stopping fluid may be infused via the bridge once for each completed anastomosis. In patients who fail PTCA, there may be coronary artery entrapment, which usually does not progress distally, and care should be taken to eliminate this entrapment during anastomosis. Re-warming is usually initiated when the last distal anastomosis is made. After opening the aortic block clamp and restarting the heart, a period of assisted circulation with low cardiac load should be performed to improve myocardial ischemia. Proximal anastomosis is feasible at this time. After arrest, low cardiac output and hypotension can be supported with vasoactive agents and IABP. Approximately 60% of patients require vasoactive support, 20% require antiarrhythmics, and 5 to 30% require IABP support for shutdown.IABP can be maintained for 24 to 48 h or until hemodynamic stabilization. In patients with refractory heart failure, ventricular assist is required, and those who do not recover cardiac function after assist should undergo heart transplantation. 4. CABG under non-CPB In recent years, CABG under non-CPB has gradually increased with the improvement of surgical instruments. In the literature (8), 35 patients underwent emergency non-CPB CABG, of which 26 were patients with grade 4 angina pectoris, 26 had 3-branch vasculopathy, 9 required preoperative IABP support, and 3 had cardiac arrest during angiography. All patients were bridged with at least one artery, 68.6% had 3 to 4 bridges and none required conversion to CPB, resulting in one death (2.9%). The main postoperative complications were supraventricular arrhythmias (22.9%) and low cardiac output (20%). Therefore, CABG under non-CPB can be considered in hemodynamically stable patients, but the total number of cases is still small and the long-term efficacy remains to be seen. (VIII) Results 1. Recent mortality The mortality rate of emergency CABG for acute MI ranged from 0 to 36%, with an average of 6%. Most of the patients were operated within 12h after the onset of chest pain. When blood flow was restored within 6 h, the near-term mortality rate was reduced to 4%, and 5% for transmural infarction. There was no difference in mortality between anterior or posterior wall infarcts. Re-emergent emergency CABG has a mortality rate of up to 47%, and results can be improved if myocardial perfusion can be improved by tethering or PTCA followed by CABG under nonemergent conditions. Recently, a literature collection of 44,365 cases of emergency CABG performed after acute MI in 32 hospitals in the United States~York State from 1993 to 96 was analyzed (9), and it was found that the mortality rate of emergency CABG performed after acute MI was high.The longer the time interval between CABG and MI, the lower the mortality rate was: 11.8% within 6 h, 9.5% from 6 h to 1 day, and 2.8% for >1 day. The difference in mortality between permeable and non-permeable MI was 3.1%. Transmural MIs have a high operative mortality rate within 7 days of acute MI. Thus, in patients with transmural MI, the surgeon should be prepared to perform cardiac support, including left heart assist, because of the high risk of early surgery. In some patients, there is a reason to wait for the right time to operate. Myocardial infarction Coronary revascularization limits the occurrence of transmural MI by reducing subendocardial myocardial necrosis and preserving viable subepicardial myocardium. About 50% of patients who underwent emergency CABG for acute ischemia had myocardial necrosis on enzymatic examination, and 20-40% had wall-permeable MI on electrocardiogram.Postoperative MI was significantly correlated with preoperative ischemic status, and the incidence of postoperative MI was significantly increased in patients with left main stem stenosis and reoperation. On long-term follow-up, the probability of recurrent MI in those who underwent emergency CABG for acute MI was 12%. The probability of recurrent MI is 12% in those who underwent emergency CABG for acute MI. 80% of those who underwent emergency CABG for failed PTCA had no recurrence of MI within 5 years and did not need CABG again. 3. Left ventricular function The left ventricular function was significantly improved in those who had complete restoration of the myocardial blood supply after surgical operation. The time to restore blood supply is an important factor: those who recover within 6 h have the best mean ejection fraction, especially in areas without collateral or side branch flow. CABG for acute MI also prevents or limits the development of post-infarction mechanical complications such as ventricular rupture, septal perforation, and mitral regurgitation. 4. Long-term survival The long-term survival rate after emergency CABG is 90-95% at 5 years and 80% at 10 years. The 5-year survival rate for those who undergo emergency CABG after PTCA is 90%. Long-term survival is lower in those with transmural MI and repeat emergency CABG. Emergency CABG is especially relevant for patients with cardiogenic shock, when the mortality rate of drug treatment is 80-90%, while 60% of those who have surgery can be discharged, and the 2-year survival rate is 90% among survivors. 5. Angina relief rate After emergency CABG, 70% of patients are completely free of angina again, and 25% of patients have angina only at maximum activity. Recurrence of angina 3 years after thrombolytic therapy or PTCA was 30%. Results after re-emergent emergency CABG were less favorable, with 80% of patients experiencing recurrent ischemia at 2 years. (IX) Conclusions The outcome of emergency CABG after acute MI has improved with lower mortality. Those who regained blood flow within 1 h of ischemia had a low incidence of transmural MI, good improvement in left ventricular function, and long-term follow-up showed fewer complications and a significantly longer time free of angina and recurrence-free MI. Emergency CABG can also be used in combination with thrombolysis and PTCA in the treatment of acute MI with lower mortality. In the era of thrombolysis and ever more skillful percutaneous puncture techniques, emergency CABG is often overlooked. It should be noted that some patients are difficult to cure with other skilled techniques, when emergency CABG is the best option.