Clinical significance of myocardial enzyme spectrum

People know very little about the myocardial enzyme spectrum, which is composed of LD, AST, CK, CK-MB and HBD. In medicine, people use the level of myocardial enzyme index to judge the development of some diseases, which is of great practical significance. What is the clinical significance of myocardial enzyme spectrum? Today I will introduce to you the clinical significance of myocardial enzyme spectrum.

The clinical significance of myocardial enzyme spectrum is mainly reflected in its important role in diagnosing myocardial infarction.

The serum LD/HBD ratio of healthy adults is 1.3-1.6, but the serum HBD activity of patients with myocardial infarction increases and the LD/HBD ratio decreases to 0.8-1.2. When liver parenchymal cells are damaged, the ratio may increase to 1.6 to 2.5. It should be noted that these ratios are not related to the measurement methods or measurement conditions of each laboratory, and the ratios of this laboratory must be established. In addition, in active rheumatic myocarditis, acute viral myocarditis, hemolytic anemia, etc., due to the increase in LD1 activity, HBD activity may also increase.

Myocardial enzymes are a general term for various enzymes present in the myocardium, including aspartate aminotransferase (AST), lactate dehydrogenase (LD or LDH), creatine kinase (CK) and its isoenzymes, α-hydroxybutyrate dehydrogenase (α-HBD), etc. During acute myocardial infarction, various enzymes are released in the myocardium due to myocardial cell necrosis. Therefore, the determination of myocardial enzymes in serum is of certain value in diagnosing acute myocardial infarction and evaluating the effect of thrombolysis.

Clinical significance

1. Creatine kinase (CK) and its isoenzymes

(1) During myocardial infarction, serum CK levels increase significantly, starting to rise 2 to 4 hours after the onset of myocardial infarction, reaching a peak in 24 to 36 hours, and returning to normal in 3 to 5 days. The increased CK in patients with myocardial infarction is mainly creatine kinase isoenzyme (CK-MB). The sensitivity of CK-MB for the early diagnosis of acute myocardial infarction (AMI) is significantly higher than that of total CK, with a positive detection rate of up to 100% and high specificity. CK-MB generally increases 3 to 6 hours after the onset of AMI, reaches a peak at 16 to 20 hours, returns to normal in 3 to 4 days, and the degree of increase is basically consistent with the size of the infarct area. In addition, the peak time of thrombolytic protein CK-MB shifted forward, indicating successful thrombolysis and opening of blood vessels.

(2) Other myocardial injuries, such as angina pectoris, pericarditis, cardiac surgery, radiofrequency ablation, and pacemaker implantation, can also increase CK-MB.

(3) CK increases in progressive muscular dystrophy, polymyositis, skeletal muscle injury and systemic convulsions, mainly in the form of muscle creatine kinase isoenzyme (CK-MM).

(4) In cases of cerebrovascular accident, brain surgery, or severe smooth muscle injury such as intestinal obstruction, elevated levels of brain creatine kinase isoenzyme (CK-BB) may be observed.

(5) The thyroid gland can inhibit the activity of CK. Serum CK may be elevated in patients with hypothyroidism, while serum CK may be reduced in patients with hyperthyroidism.