What can be ruled out if myocardial enzymes are normal

I believe everyone has heard the saying that no matter whether you are rich or poor, you should not get sick. Illness really makes people hate it, but sometimes they are helpless. People all hope that their bodies are normal, but often the results are far from satisfactory. For example, the myocardial enzyme index in our human body. If the myocardial enzyme is abnormal, it will cause many diseases. So today I will give you a brief introduction on what normal myocardial enzymes can exclude.

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.

If the myocardial enzyme is normal, myocardial infarction can be ruled out. If the mood changes significantly during a myocardial infarction, panic attacks usually manifest as precordial pain accompanied by squeezing pain in the back. Thrombolytic therapy is needed as soon as possible, and some nitroglycerin should be used for treatment at the same time. Stents should be placed when necessary.

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.

(6) Serum CK increases after strenuous exercise.

2. Lactate dehydrogenase

(1) Increased LD is mainly seen in acute myocardial infarction, viral hepatitis, cirrhosis, pulmonary infarction, skeletal muscle disease, leukemia, especially acute lymphocytic leukemia and pernicious anemia. When diagnosing acute myocardial infarction, LD reaches its peak 12 to 24 hours after onset and can continue to rise for up to 10 days.

(2) LD may increase when a malignant tumor develops to a severe stage. LD may also increase in pleural effusion and ascites caused by the tumor.

(3) In patients with chronic glomerulonephritis, systemic lupus erythematosus, or malignant tumors of the bladder or kidney, the LD50 in the patient's urine may increase to 3 to 6 times that of normal controls.

(4) In patients with subarachnoid hemorrhage, cerebral vascular thrombosis and bleeding, LD in cerebrospinal fluid is elevated.

(5) A decrease in LD is meaningless.