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Troponins are contractile proteins of striated muscles (skeletal and heart muscle). Troponin testing is recommended in order to identify or rule out an infarction or other myocardial injury. Troponins rise in the three hours following a myocardial infarction.
Characteristics of troponin I and T
Troponins I and T are muscle contractile proteins found in skeletal and cardiac muscles. In addition to these two troponins, there is also troponin C. All three are responsible for regulating muscle contraction. Meanwhile, cardiac troponins are:
- sercoin troponin T (cTnT),
- cardiac troponin I (cTnI).
They are the most studied. They get into the blood when muscle cells are damaged, for example during a myocardial infarction. The higher the concentration of troponins in the blood, the larger the area of the muscle affected by the infarction. Troponin I and T tests are performed on a blood sample taken from the patient.
When do we perform troponin I and T tests?
The most important indication for the determination of troponin I and troponin T is the occurrence of symptoms suggesting a myocardial infarction. The most common symptoms of this ailment are chest pain, which can be distressing and pressing. It can affect the area of the left shoulder, neck, lower jaw and even the back. The characteristic feature of a heart attack is the lack of relief after administration of nitroglycerin. These symptoms require a quick response and medical attention as well as a troponin determination, which should be performed three times (immediately after the appearance of pain, then 3-6 hours and then 9-12 hours). Troponin I and T testing is also ordered:
- in the diagnosis of chest pain.
- when skeletal muscle damage is suspected,
- in patients with worsening of the angina. This ailment (especially unstable) increases the risk of developing ischemic heart disease and a future heart attack.
Troponin I and troponin T – study
The troponin test is performed immediately after the patient arrives at the ward with a suspected heart attack. They should be repeated after 3-6 and 9-12 hours.
Material for the study of troponin: serum.
Preparation for the test: it does not require special preparation.
The course of the study: one-time blood sampling from a vein in the arm. The injection area is cleaned with an antiseptic. Then the blood is analyzed in a special device. Usually, a test for the presence of one of the troponins is performed, as both tests are equivalent. In order to maintain all safety measures, the staff should be informed about the possible carrier of sexually transmitted viruses, such as HIV, HBV or HCV. With this knowledge, additional safety measures will be implemented to prevent further disease transmission.
Time to wait for the result: 1 hour.
Standard: less than 0,1 ng / ml. These values can vary depending on several factors:
– age
– gender
– determination methods.
However, it is assumed that the correct result is one that does not exceed 0,1 ng / ml. However, the interpretation should always be left to the doctor. T.
Cardiac troponins are found in the blood in small amounts also under normal conditions. Accordingly, the upper limits of the norm have been established. They are:
— troponin I (cTnI) – 0,014 μg/L,
— troponin T (cTnT) – zakres 0,009–0,4 μg/L.
Comments: The increase in troponin concentration is observed 3-8 hours after the myocardial infarction. The highest values occur 12-72 hours after the infarction, and the normalization occurs after 7-14 days. To determine the time of myocardial infarction, the concentration of troponins and the activity of creatine kinase – total and its MB isoenzyme are usually determined. The increase in troponin concentration can also be noticed in the case of vascular events of the central nervous system (stroke, haemorrhage) and in patients with chronic renal failure.
Troponins – how to interpret the results?
Elevated cardiac troponins usually indicate damage to the heart muscle. The more the values are exceeded, the greater the damage. However, a one-time test is not enough to diagnose a heart attack. The change in troponin levels should be monitored. For this reason, the test is performed three times (as mentioned above). In a situation where the high concentration is kept constant, other causes should be looked for. High troponin can also be the result of:
- prolonged physical exertion (e.g. running a marathon),
- pulmonary hypertension,
- abnormally fast heart rate,
- myocarditis,
- strong heart palpitations,
- congestive heart failure,
- pulmonary embolism (blockage of the pulmonary artery by a clot in blood, fat, or cancer cells)
- coronary artery spasm,
- aortic dissection,
- side effects of the medications you take,
- mechanical damage to the heart,
- cardiomyopathies,
- aortic valve defects.
Also, some procedures, such as defibrillation, coronary angioplasty, kradioversion or open-heart surgery – may cause elevated troponin levels. Not only conditions that directly affect the heart increase troponin levels. One should not forget about ailments that may cause secondary damage to the heart:
- sarcoidosis and amyloidosis,
- sepsis,
- heavy gastrointestinal bleeding
- Burns,
- stroke,
- kidney failure
- respiratory failure,
- hemochromatoza,
- subarachnoid hemorrhage.