Myocardial ischemia (myocardial ischemia) refers to a pathological state in which the blood perfusion of the heart is reduced, resulting in reduced oxygen supply to the heart, abnormal myocardial energy metabolism, and inability to support the normal work of the heart. The energy required for cardiac activity is almost entirely provided by aerobic metabolism, so even at rest, the blood oxygen uptake rate of the myocardium is very high (about 70%). Under normal circumstances, the body can regulate itself to promote blood supply and demand. Relatively constant, ensuring the normal functioning of the heart. When some reason causes an imbalance between myocardial blood supply and demand, it constitutes true myocardial ischemia. Coronary heart disease is the most important and common cause of myocardial ischemia. With the improvement of people's living standards, the prevalence of myocardial ischemia in our country has been increasing year by year, and has become a common and frequently-occurring disease in middle-aged and elderly people. Some young people aged 20 to 30 also show symptoms of myocardial ischemia. .