Creatine kinase isoenzymes (creatine kinase isoenzymes) alias serum creatine kinase isoenzymes, according to different forms can be divided into: muscle type (CK-MM), brain type (CK-BB), hybrid type (CK-MB) and mitochondrial type (CK-MiMi) four types. Normal human tissues usually contain three types of creatine kinase isoenzymes, CK-BB, CK-MB, CK-MM. CK-BB is mainly found in brain, kidney and uterine tissue, and is almost absent in serum; Among them, CK-MB mainly exists in myocardial tissue, accounting for 0-4% of CK in serum; CK-MM is mainly present in skeletal muscle, accounting for 96%?100% of CK in serum. When cardiomyocytes are damaged, serum levels of CK-MB and CK-MM are elevated, but because the myocardium is the only organ in the human body that contains the most CK-MB, about 15-40%, CK-MB is more myocardial specific.