I. What is coronary heart disease? Coronary heart disease is one of the common diseases in cardiovascular disease, which often occurs in middle-aged and elderly people. It is caused by the narrowing and occlusion of the coronary arteries that supply blood to the heart due to atheromatous plaque, resulting in the reduction or even partial interruption of blood supply to the heart, thus causing myocardial ischemia, hypoxia and even necrosis. Depending on the severity of the ischemia, patients may suffer from angina pectoris, myocardial infarction, arrhythmia, congestive heart failure and other conditions. In severe cases, complications such as ventricular wall tumor, septal perforation, papillary muscle dysfunction, heart rupture, and even sudden death can occur. Second, what tests should be done before coronary heart disease surgery? Before coronary artery disease surgery, in addition to routine electrocardiogram, echocardiogram and X-ray examination, isotope, ultra-high speed CT and coronary artery angiography may be required. Selective coronary angiography is performed by inserting a catheter through the brachial artery to the ascending aorta, positioning the catheter with the aid of X-ray fluoroscopy, inserting the catheter into the left and right coronary artery openings located at the root of the aorta, and then injecting contrast to visualize the coronary arteries and their branches. The catheter is then injected to visualize the coronary artery and its branches to understand the site and degree of coronary artery blockage or stenosis in preparation for surgery. C. What is coronary artery bypass surgery? Coronary artery bypass surgery is to anastomose the internal mammary artery or gastroretinal artery with the distal end of the blocked coronary artery or to take a section of autologous saphenous vein or other vessels located in the leg and make a bypass between the ascending aorta and the distal end of the blocked coronary artery, so that the blood from the aorta can be supplied to the distal end of the coronary artery through the transplanted vessel to restore the blood supply to the corresponding myocardium and improve myocardial ischemia and stenosis. This restores blood supply to the corresponding heart muscle, improves myocardial ischemia and hypoxia, and relieves angina and other symptoms. This surgical procedure is called coronary artery bypass grafting. Why do we need coronary artery bypass surgery? When the stenosis of coronary artery is less than 50%, it has little effect on the blood flow, but when the stenosis reaches 75%, it will obviously affect the blood flow and produce angina symptoms. Therefore, any single coronary artery with a stenosis of 75% or two or more stenoses greater than 50% requires coronary artery bypass surgery. Many patients who have undergone coronary angioplasty and have stents installed in their coronary arteries (commonly known as PTCA) also require timely bypass surgery once angina occurs again. This will not only eliminate angina and enable the patient to live and work normally, but also prevent myocardial infarction and sudden death. The reconstruction of blood flow in diseased coronary arteries restores blood supply to the heart muscle, improves ischemic symptoms and enhances the quality of life. If severe coronary artery disease is left untreated, there is a risk of acute myocardial infarction, which can produce complications such as ventricular wall tumors, septal perforation, papillary muscle dysfunction, heart rupture, and even sudden death.