What Is Troponin?

Troponin (Tn) is a protein that regulates the contraction of muscle tissues. It is located on the thin filaments of contractile proteins and plays an important role in muscle contraction and relaxation. It contains three subtypes: fast response and slow response. And cardiac troponin (cTn). The first two are related to skeletal muscle, while cardiac troponin is only found in cardiomyocytes. It is composed of three subunits: troponin T (cTnT), troponin I (cTnI), and troponin C (cTnC). Composition of the complex. cTnT and cTnI are specific antigens of cardiomyocytes. The molecular weight of cTnI is about 23.88 KDa, which is degraded from myocardial fibers when cardiomyocytes are damaged. The increase of cTn in serum reflects the damage of cardiomyocytes, and its specificity and sensitivity are higher than the myocardial enzyme spectrum commonly used in the past. [1]

cTnT <0.1 g / L is normal;> 0.2 g / L is the diagnostic threshold;> 0.5 g / L can be diagnosed as acute myocardial infarction; cTnI <0.2 g / L is normal;> 1.5 g / L is the diagnostic threshold ( Using ELISA method). [1]
Troponin is a marker of myocardial injury and necrosis, and has important clinical significance for the diagnosis and risk stratification of acute myocardial infarction (diagnostic sensitivity 100%, specificity 91%, and long duration). Increased troponin value indicates myocardial injury, which can be seen in acute myocardial infarction, unstable angina pectoris, pulmonary infarction, heart failure shock and other diseases that cause myocardial injury such as pancreatitis, severe diabetic ketoacidosis, connective tissue disease, The higher the value, the wider the range of damage. In patients with acute myocardial infarction, release begins at 3 to 6 hours, peaks at 10 to 24 hours, and the normal time to recovery is 10 to 15 days and 5 to 7 days; part of renal function. Patients with insufficiency can also appear elevated. [2]
Since foreign reports of troponin detection in peripheral blood in 1987 to diagnose myocardial infarction, troponin has gradually replaced creatine kinase isoenzyme (CK-MB) as a gold indicator of biochemical markers of myocardial infarction within about 10 years. Calcium protein is of great significance in the screening, diagnosis and judgment of the prognosis of acute myocardial infarction in chest pain in emergency department, and its advantages are reflected in the following three points: [1]
1. High specificity: troponin is basically expressed only in the myocardium, which means that myocardial injury is higher, which is more myocardial specific than CK-MB. [1]
2. Smaller molecular weight and longer duration: When the myocardium is damaged, it is easier to diffuse out of the myocardial cells and can be detected earlier. At the same time, the advantage of long duration makes more recent myocardial infarctions not to be missed. [1]
3 High correlation between the concentration and the degree of injury: different concentrations reflect different degrees of myocardial necrosis, and its dynamic detection is very helpful for judging the prognosis. In addition, it is worth mentioning that during renal insufficiency, the plasma clearance of troponin-degraded small fragments decreases, which makes some patients without myocardial ischemia also increase. Judgment of patients with renal insufficiency needs to be cautious. [1]

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