CKMB refers to creatine kinase isoenzyme, which mainly lies in the heart tissue and is involved in intracellular energy operation. If CKMB is significantly elevated, it suggests the presence of myocardial cell necrosis and is considered to be acute viral myocarditis or acute myocardial infarction. CKMB is also elevated when there is skeletal muscle injury or progressive myotonic dystrophy. Currently, creatine kinase isoenzymes are mainly used in clinical practice for the diagnosis of myocardial infarction, and a rapid elevation of creatine kinase is more valuable in the diagnosis of myocardial infarction than an electrocardiogram. In myocardial infarction creatine kinase is elevated within 6 hours and peaks at 24 hours. The diagnostic specificity of creatine kinase isoenzyme is highest. CKMB can be measured in patients with long-term coronary artery disease if they have large precordial pain and if nitroglycerin is not effective.