Troponin

The troponin value is mainly used to diagnose a heart attack. Read more about the troponin test and its importance!

Troponin

troponin is a protein complex found in various forms in skeletal and cardiac muscle cells. It is an important laboratory value in the diagnosis of heart damage. Read all important information about muscle protein, its structure and function and when it reaches critical levels!

Product Overview

troponin

  • What is troponin?

  • When do you determine troponin?

  • Troponin-standard values

  • When are the troponin levels lowered?

  • When are the troponin levels increased?

  • What to do with modified troponin?

What is troponin?

Troponin is an important muscle protein: Skeletal and heart muscles are - albeit in different ways - made up of muscle fibers (myocytes, muscle cells). Each muscle fiber consists of up to hundreds of muscle fibrils (myofibrils) containing filamentous strands (myofilaments). These strands contain a variety of proteins that help muscles contract and relax. One of these proteins is troponin.

What is troponin exactly?

There are basically three different troponins. They are composed of amino acids and form protein complexes. These consist of three subunits each. The subunit (UE) troponin C binds calcium. The UE troponin T docks to another protein (tropomyosin), as well as the UE troponin I, which is superimposed on the structural protein actin. Their interaction allows muscles to contract and relax. The three troponin complexes of the body are:

  • the heart troponin (consists of subunits cTnT, cTnI, TN-C)
  • the troponin of the white skeletal muscle (for fast movements, consists of the UE fTnT, fTnl, TN-C2)
  • Troponin of red skeletal muscles (for muscular endurance, consists of the UE sTnT, sTnI, TN-C).

Meaning in medicine

In medicine, the determination of muscle protein in particular on the two protein complexes troponin T (cTnT = cardiac troponin T) and troponin I (cTnI = cardiac troponin I), which occur only in cardiomyocytes. Experts therefore count them among the so-called biomarkers. Biomarkers are endogenous substances (such as proteins or metabolites) that are suitable for making statements about disease processes in the body. For example, in a heart attack, troponin acts as a biomarker of heart damage.

When do you determine troponin?

If the doctor has the suspicion that the heart muscle of a patient is damaged, he determines troponin T and troponin I (in addition, he makes compelling a so-called 12-channel ECG). In addition to these two laboratory values, the doctor also measures other endogenous substances that are elevated after a heart attack. These include various protein structures such as myoglobin and the enzymes creatine kinase (CK and CK-MB), lactate dehydrogenase (LDH) and glutamate-oxaloacetate transaminase (GOT = AST). However, these substances also occur in other body cells, so they are not heart specific. In everyday clinical practice, physicians classify the named substances under the term "heart enzymes".

In addition, medics are using troponin to detect a rejection response after heart transplantation. Even with heart muscle damage, which is due to an organ failure elsewhere (especially the kidney), they determine the Troponinwert.

Troponin test

For Troponinmessung the doctor takes the patient from a blood sample, which is then analyzed in the laboratory.

In addition, there are also Troponin tests that can be performed directly on the bed of the patient. Since their results are often inaccurate than the measured values ​​from the laboratory, they are primarily used to control the course of the measured values.

Thanks to recent developments, there are meanwhile even more sensitive test procedures, so-called highly sensitive Troponin T tests. This troponin T hs (hs = highly sensitive) can detect an acute myocardial infarction even earlier than previously. Because conventional tests make it difficult to detect muscle protein shortly after a heart attack (increase only measurable after about three hours).

Troponin test in heart attack

A heart attack (myocardial infarction) occurs when a blood vessel of the heart (coronary vessel or coronary vessel) narrows or completely closes due to deposits on the inner walls. The heart muscle is then no longer (sufficiently) supplied with oxygen and can no longer do its work. Patients experience a strong feeling of pressure, burning or pain behind the sternum (angina pectoris), possibly radiating to the arms, neck, jaw, upper abdomen or back.

When a heart attack is suspected, doctors perform an electrocardiogram (ECG) as soon as possible. If there are typical changes in the infarction (such as ST elevations), they initiate measures to restore the coronary blood flow (revascularization).

If the ECG shows no abnormalities, a heart attack is not yet ruled out (such as in a so-called NSTEMI). In this case, troponin comes into play as the most important infarct biomarker. However, as it only increases after some time (and thus may still be normal shortly after a possible heart attack), doctors control the blood level of the heart muscle protein several times at frequent intervals. Doctors use troponin T hs tests because they can detect myocardial damage very early.

Control of the course

Troponin increases in the first hours after heart damage. It reaches its peak after about 12 to 96 hours. It takes about six days to two weeks before the values ​​recover. Therefore, doctors also determine the heart muscle protein to check the course of a heart muscle disease or the success of a therapy (such as revascularization).

Troponin-standard values

Which standard troponin values ​​apply depends on the test procedure. Highly sensitive tests can detect even the smallest amounts of heart muscle protein in the blood. Therefore, there are other troponin T standard values ​​as in conventional assay procedures.

Troponin T / troponin I

Troponin T hs (highly sensitive)

normal values

<0.4 μg / L

<14 ng / L (<0.014 μg / L)

(<0.014 ng / ml; <14 pg / ml)

Suspected heart muscle disease, infarction not excluded

0.4-2.3 μg / L

14-50 ng / L (0.014-0.05 μg / L)

(0.014-0.05 ng / ml, 14-50 pg / ml)

Suspected heart attack

> 2.3 μg / L

> 50 ng / l (> 0.05 μg / L)

(> 0.05 ng / ml;> 50 pg / ml)

When are the troponin levels lowered?

Troponin is located in the heart muscle cells. It will only be released if it is damaged. Therefore, the heart muscle protein in the blood of healthy people is usually undetectable. Sometimes, metrologically, slightly elevated values ​​can be found (but still within normal values).

When are the troponin levels increased?

Even mildly damaged heart muscle cells lead to a Troponinerhöhung. Causes of these elevated levels are:

  • Heart attack (myocardial infarction), general: acute coronary syndrome (unstable angina pectoris, NSTEMI, STEMI)
  • Tachycardia with arrhythmias (tachycardiac arrhythmia)
  • dangerous blood pressure increase (hypertensive crisis)
  • Heart failure (heart failure)
  • Myocarditis (myocarditis)
  • Heart muscle diseases such as Tako-Tsubo cardiomyopathy (malfunction due to mental or emotional stress, also called "broken-heart" syndrome)
  • Tear of the main artery wall (aortic dissection), severely narrowed main artery (aortic stenosis)
  • Pulmonary embolism, pulmonary hypertension (pulmonary hypertension, damage to the heart due to blood back pressure)
  • Heart surgery, heart transplants

Less often, other factors increase when troponin is elevated in the blood of a patient. Among other things, the following reasons lead to a troponin T increase, especially in highly sensitive tests:

  • Spasm of the coronary arteries (coronary spasm)
  • Inflammation of the heart disease (coronary vasculitis)
  • neurological disease events such as stroke or cerebral hemorrhage
  • slight damage to the heart through medical interventions such as bypass surgery, cardiac catheterization, pacemaker excitation, electroshock (for resuscitation or normalization of the heart rhythm = cardioversion)
  • Thyroid hypofunction (hypothyroidism) and hyperthyroidism (hyperthyroidism)
  • heart-damaging drugs (e.g., chemotherapeutic agents such as doxorubicin)
  • Poisons (like snake venom)
  • Blood poisoning (sepsis)

What to do with modified troponin?

Altered or elevated troponin levels must always be viewed critically. They point to damaged heart muscle cells. The higher the blood level of the heart muscle protein, the higher the probability of heart damage and the worse the prognosis of the patient. Therefore, physicians act fast on elevated troponin to avoid serious consequences such as fatal cardiovascular failure. In addition, they take blood at regular intervals in order to monitor the course of the disease and the success of the therapy on the basis of the troponinLevel control.


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