Some patients showed severe arrhythmias and cardiac insufficiency after coronary artery reperfusion, and animal experiments proved that this phenomenon is closely related to myocardial ischemia and reperfusion, which is called myocardial ischemia-reperfusion injury. Myocardial ischemia-reperfusion injury manifestations: 1, arrhythmia: may be related to reperfusion intracellular calcium overload and extracellular potassium ion reduction. 2, intracellular calcium overload. 3, ultrastructural changes: sudden edema of blood perfused cardiomyocytes, plasma membrane disruption, mitochondrial swelling and rupture, myofiber contraction and necrosis. 4.Increased cardiac enzyme leakage: creatine kinase and low-density lipoprotein are increased in reperfused coronary artery, venous sinus and body venous blood. 5.No reflux phenomenon: swelling of endothelial cells and leukocyte blockage of some small vessels in the perfusion area are common in the non-reflux state. 6, acute myocardial edema: myocardial compliance is reduced. 7.Decreased cardiac function: manifested by decreased ventricular compliance, contractility, blood pressure, etc., and in severe cases, unable to support the circulation.