The cause of sudden myocardial infarction is the result of a combination of endogenous and exogenous factors. The endogenous cause is the underlying etiology, most of which are coronary atherosclerosis, and unstable plaques, and a few are due to persistent vascular spasm. Under the action of certain exogenous factors, that is, the causative factors, the unstable atheromatous plaque will rupture, bleeding, and thrombosis, resulting in one or more vessel lumen narrowing, or complete occlusion, while the collateral circulation has not been fully established, so that the blood supply is sharply reduced or interrupted, and the myocardium will be severely and persistently acute ischemia. If the ischemia reaches 20-30 minutes or even longer, myocardial necrosis and myocardial infarction results.