High isoenzyme refers to elevated serum creatine kinase isoenzyme, which is a special form of phosphocreatine kinase present in brain tissue, cardiac tissue and skeletal muscle. Diseases that cause elevated serum creatine kinase isoenzyme include acute myocardial infarction, myocarditis, cerebrovascular accident or skeletal muscle injury due to trauma. When patients have symptoms of chest tightness and chest pain, serum phosphokinase isoenzyme should be tested promptly. It starts to rise 2-4 hours after the occurrence of heart attack, reaches its peak at 24 hours, and gradually returns to normal level at 48 hours. When the value of isoenzyme is higher than 3 times or more than the normal value, the possibility of myocardial infarction should be seriously considered, and the values of troponin and myoglobin should be checked, and electrocardiogram should be examined, so that a clear diagnosis can be made in time and corresponding treatment can be given in time.