Stable angina has five characteristics, namely pain triggers, pain site, pain nature, duration, and relief mode, as follows: 1, stable angina triggers, such as exercise, emotional excitement, physical activity, etc.; 2, the nature of pain, generally boring pain, not particularly intense, or not accompanied by sweating; 3, pain duration is generally 3-5 minutes, or less than 1 minute, if more than 20 minutes to consider myocardial infarction; 4, pain relief mode is generally the same, such as containing heart pills can be relieved after 3 minutes.