MB and myocardial ischemia: These macromolecular substances are known as myocardial-injury biochemical markers, including creatine kinase (CK-Mb), glycogen phosphorylase isoenzyme (PYGB), myoglobin (MB), cardiac troponin (cTn), etc. PYGB is sensitive to myocardial ischemia and hypoxia, and it may become an indicator for the early diagnosis of ACS, filling the deficiencies of the traditional markers of myocardial injury.