Interpret the 3 major markers for detecting myocardial damage

The main biochemical markers that reflect myocardial ischemia injury include myocardial enzymes and myocardial proteins. Myocardial enzymes mainly include serum aspartate aminotransferase, serum lactate dehydrogenase and its isoenzymes, serum creatine kinase and its isoenzymes Enzymes; Myocardial proteins mainly include troponin, myoglobin, etc. Today, we mainly introduce three major markers related to myocardial enzymes.

1. Serum aspartate aminotransferase

Aspartate aminotransferase (AST), also known as aspartate aminotransferase (GOT), is widely distributed in various tissues of the human body. It is rich in liver, skeletal muscle, kidney and heart muscle. Red blood cell AST is about 10 times that of serum, and mild hemolysis will increase the measurement result.

(1) Reference value: <40U/L (37℃), usually using enzyme coupling rate method.

(2) Clinical significance: AST increases 6 to 12 hours after the occurrence of acute myocardial infarction, reaches a peak value of 24 to 48 hours, lasts for 5 days or 1 week, and then decreases. Because AST is not tissue-specific, elevated AST alone cannot diagnose myocardial injury.

2. Serum lactate dehydrogenase and its isoenzymes

Lactate dehydrogenase (LD) is a key enzyme that regulates the conversion of pyruvate to lactic acid in the anaerobic glycolysis of glucose. It is widely present in the cytoplasm and cytoplasm of tissue cells such as liver, heart, skeletal muscle, lung, spleen, brain, red blood cells, and platelets. Mitochondria. LD is a tetramer with a molecular weight of 135KD. It is composed of M-type and H-type subunits to form 5 isoenzymes: H4 (LD1), MH3 (LD2), M2H2 (LD3), M3H (LD4), M4 (LD5).

(1) Reference value:

①Lactate dehydrogenase: 200～380U/L when pyruvate is the substrate; 109～245U/L when lactic acid is the substrate.

②LD1 is 28.4%±5.3%, LD2 is 41.0%±5.0%, LD3 is 19.0%±4.0%, LD46.6%±3.5%, LD5 is 4.6%±3.0%. The total activity of lactate dehydrogenase is usually measured by rate method, and its isoenzyme is usually measured by electrophoresis.

Clinical significance: When myocardial injury occurs, myocardial cell membrane ruptures, and mitochondria and cytoplasmic substances leak into the intercellular fluid and peripheral blood. Lactate dehydrogenase and its isoenzyme LD1 begin to increase 8-12 hours after the onset of acute myocardial infarction, reach a peak at 48-72 hours, and return to normal within 7-12 days. Continuous determination of lactate dehydrogenase has certain reference value for patients with acute myocardial infarction whose creatine kinase has returned to normal after seeing a doctor.

3. Serum creatine kinase

Creatine kinase (CK) is an important energy regulating enzyme in the myocardium. Under the energy provided by ATP, it catalyzes the production of creatine phosphocreatine and ADP. Creatine kinase is mainly distributed in skeletal muscle and myocardium, followed by the cytoplasm and cytoplasm of brain tissue. Mitochondria.

(1) Reference value: enzyme coupling method or continuous monitoring method, male 38～174U/L, female 26～140U/L; creatine color method, male 15～163U/L, female 3～135U/L.

(2) Clinical significance:

①Diagnosis of acute myocardial infarction: Creatine kinase rises significantly 3 to 8 hours after the onset of acute myocardial infarction, reaches a peak at 10 to 36 hours, and returns to normal in 3 to 4 days. If creatine kinase is less than the upper limit of the reference value, acute myocardial infarction can be excluded, but small-scale myocardial injury and subendocardial infarction should also be excluded.

② Creatine kinase is significantly increased in viral myocarditis.

③ Polymyositis and skeletal muscle damage caused by various reasons, various intubation and post-operation, intramuscular injection of chlorpromazine, etc., creatine kinase can be increased.

Acute myocardial infarction is an acute cardiovascular disease that will seriously affect the health and life safety of patients. Early diagnosis and early treatment are the key to reducing the mortality rate and improving the prognosis of patients. The three markers introduced above are useful for detecting myocardial injury, Acute myocardial infarction, myocarditis and other myocardial diseases have important values. They not only have high sensitivity and a short diagnostic window, but also provide effective guidance for clinical treatment. They are currently recognized myocardial markers with high specificity.