Troponin test in the diagnosis of myocardial infarction

This is an automatically translated article.

The article was professionally consulted by Specialist Doctor II Nguyen Quoc Viet - Department of Medical Examination & Internal Medicine - Vinmec Danang International General Hospital. The doctor has more than 20 years of experience in the examination and treatment of cardiovascular diseases and Interventional Cardiology.
Troponin is a protein released when the heart muscle is damaged. Currently, high sensitive troponin tests are recommended to be used, replacing the previous Troponin test. Due to its high sensitivity, the ultra-sensitive Troponin test helps to detect the early rise of Troponin, helping to diagnose early and avoid missing the disease.

1. What is Troponin?

Troponin is a globular protein found in skeletal and cardiac muscle with three functional subunits: Troponin I (TnI), Troponin T (TnT), and Troponin C (TnC). Troponin mediates the interaction between actin and myosin that regulates muscle contraction. In the heart, Troponin helps the heart muscle contract. The genes encoding the Troponin C isoforms in bone and muscle are not structurally different. But the troponin I and T isoforms in skeletal and cardiac muscle are distinct and can be detected by immunoassays. Normally, cardiac-specific troponin (cardiac TnT abbreviated cTnT and cardiac TnI abbreviated cTnI) in the blood is very low, when the myocardium is necrotic, after a few hours, cardiac-specific troponin is released into the blood and can can be maintained for up to two weeks. Because of its myocardial specificity and maintained high for many days, Troponin T and I tests are widely used, playing an important role in the detection of myocardial damage.

2. What is a normal Troponin T?

Currently, high sensitive troponin tests are recommended to be used, replacing the previous Troponin test. Due to its high sensitivity, the ultra-sensitive Troponin test helps detect the early rise of Troponin, helping to diagnose early and avoid missing the disease. When using the ultra-sensitive Troponin test, the process of diagnosing or ruling out acute myocardial infarction requires only 3 hours, compared to 6-9 hours as before.
The highly sensitive Troponin T test (hs-cTnT) quantified by ECLIA immunoassay has been used in major hospitals across the country. Normal Troponin T:
People under 50 years old: Plasma hs-cTnT concentration <14 ng/L People 50-75 years old: Plasma hs-cTnT concentration <16 ng/L People >75 years old: Plasma hs-cTnT concentrations <70.6 ng/L However, normal Troponin T values ​​may vary between laboratories due to different reagents and machines used. If previous quantitative cTnT assays detected only relatively large cTnT values ​​(from 0.10 μg/L), the ultra-sensitive Troponin assay with a cross-sectional value of 14 ng/L can detect all forms. Mild myocardial damage occurs in chronic conditions such as arrhythmia, pulmonary embolism,...

3. Troponin test in diagnosis of myocardial infarction

The cardiac troponin T test is often indicated for the diagnosis and monitoring of acute coronary syndromes including acute ST-segment elevation myocardial infarction, non-ST-segment elevation myocardial infarction, or angina pectoris. hs-cTnT is the test indicated immediately upon admission of patients with suspected acute coronary syndromes.
If hs-cTnT results are normal (<14 ng/L) on the first test, a second test must be repeated after 3-6 hours, if hs-cTnT increases by more than 50% from the value Initial myocardial infarction, if the result is still <14 ng/L, there is no myocardial infarction. If the initial hs-cTnT is moderately elevated from 14-53 ng/L, a second test is performed 3-6 hours later, if the hs-cTnT result is increased by more than 50% from baseline, myocardial infarction is indicated. grant. If the initial hs-cTnT > 53 ng/L still requires a second test after 3-6 hours, if the hs-cTnT rises more than 30% from the baseline value, an acute MI is confirmed. In the elderly, the Hs-cTnT result of 86.8 ng/L is an effective value for the diagnosis of acute myocardial infarction. To diagnose the disease, in addition to the cardiac-specific Troponin test results, doctors also rely on clinical symptoms, electrocardiogram results, echocardiography, etc. Because in addition to myocardial infarction, Troponin is heart-specific. also increased in some other diseases such as chronic kidney failure, acute pericarditis, acute pulmonary embolism, severe acute heart failure, myocarditis, septic shock,...
In addition to being used to diagnose and monitor the association In acute coronary artery disease, Troponin T test is also used to predict the severity of the disease and evaluate the effectiveness of treatment.

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