If a patient with coronary artery disease suddenly develops low blood pressure, the following conditions should be considered: 1. pay attention to the possibility of acute myocardial infarction, especially acute inferior myocardial infarction or acute right ventricular myocardial infarction, the patient shows low blood pressure and even shock performance, this situation should be properly supplemented with blood volume for expansion. 2. if coronary artery disease suddenly develops low blood pressure, also pay attention to the possibility of gastrointestinal bleeding. It is possible that patients with coronary artery disease will take anti-platelet aggregation drugs and are prone to gastrointestinal bleeding. A large amount of bleeding in the gastrointestinal tract can cause a drop in blood pressure, and in severe cases, shock can occur. 3, pulmonary infarction, patients with coronary artery disease are at risk of thrombosis, and if a pulmonary infarction occurs, a sudden drop in blood pressure can occur.