CK-MB can diagnose myocardial infarction without damaging skeletal muscle, and is also suitable for early diagnosis. Its clinical specificity is higher than myoglobin. Repeating this test at different times is helpful to diagnose AMI. After 90 minutes of thrombolytic therapy, the measured value increased by 4 times, suggesting that vascular reperfusion was successfully blocked. For patients with unstable angina pectoris, CK-MB increased, and the incidence and mortality of myocardial infarction increased significantly several months later. In addition, when the skeletal muscle is injured, the measured value will also increase, so it is very important to ask the medical history and observe the symptoms.