Isoenzymes are a subtype of creatine kinase and are more specific than creatine kinase for diagnosing myocarditis or myocardial infarction in the clinical setting. If a patient has elevated creatine kinase isoenzyme, then further clinical tests for troponin I or troponin T are required to assess whether the patient has an acute myocardial infarction, taking into account the patient’s actual symptoms and the dynamic evolution of the electrocardiogram. The isoenzymes are of great clinical importance because they help to clarify whether the patient has suffered a myocardial infarction and to further assess the extent of the current myocardial infarction. If a patient does not have an elevated isoenzyme at the beginning of angina, it is recommended that it be rechecked after 3-4 hours.