Patients with stable angina are categorized into four grades based on the severity of angina, a grading method that is based on the severity of angina developed by the Canadian Society of Cardiovascular Disease. Grade I means that the patient’s general physical activity is unrestricted and angina may occur only with more intense or rapid activity. Grade 2 means that normal physical activity or exercise is mildly restricted, but the degree of restriction is not serious, such as when the patient walks quickly in cold weather, exercises after meals, or after emotional excitement, angina symptoms may occur, and if the walking distance is taken into account, there is a restriction when walking more than 200 meters or climbing more than one floor of a building, but it is not particularly obvious. Grade 3 means that even if the patient engages in general physical activities or sports, it is obviously limited. If measured by walking distance or climbing stairs, the patient will cause angina symptoms within 200 meters of walking or climbing one floor of a building. Grade 4 is the most serious grade, in which angina symptoms may be triggered even when the patient is at rest or in light activities.