Troponin Levels

The term 'troponin' refers to the complex of three specific proteins that play a vital role in muscle contraction in the skeletal and cardiac muscles. The proteins that are categorized under this complex include troponin I (TnI), troponin C (TnC) and troponin T (TnT). Since this protein complex is instrumental in facilitating cardiac muscle contraction, an increase in their levels could be indicative of myocardial damage or myocardial infarction. TnI and TnT are specific to cardiac muscles which is why checking their levels can provide valuable information that may help in diagnosing disorders associated with the myocardium. A troponin test is undoubtedly a useful diagnostic test that is ordered when a person seems to be exhibiting symptoms of heart conditions such as unstable angina or a heart attack.

Function of Troponins

These regulatory proteins play a vital role in the process of cardiac muscle contraction. It is basically the change in the concentration of intracellular calcium that causes the muscles to contract and relax. TnC binds to calcium ions to bring about changes in TnI. TnT attaches to a protein called tropomyosin to form the troponin-tropomyocin complex that lies within the grooves of actin filaments. It is TnI that attaches to actin in thin filaments in muscle cells and helps in anchoring the actin-tropomyocin complex. Whenever calcium ions flow into the cytoplasm and move towards the actin and myosin filaments, they attach themselves to troponin-tropomyocin molecules. This brings about a change in the shape of troponin which in turn causes tropomyosin to move out from its place. Once actin-myosin binding sites become exposed, actin and myosin interact with each other. This causes the muscle to contract. When calcium ions are not present in the cytoplasm, troponin takes its normal shape. Since myosin and actin cannot interact due to the non-availability of the actin-myosin binding sites, the muscle relaxes.

When is Troponin Test Ordered?

Whenever the cardiac muscle gets damaged, these proteins are released into the bloodstream. Thus, doctors order a troponin test along with other diagnostic tests if a patient is exhibiting or experiencing signs of heart damage. After a heart attack, the levels of certain substances in the blood get elevated. These substances are referred to as cardiac biomarkers. The cardiac biomarkers include troponin, creatine kinase, myoglobin and one of the creatine kinase isoenzyme (CK-MB). Elevated levels can be detected within four hours of the heart muscle injury. Whenever doctors suspect the patient to be having a heart attack, this test is carried out several times in the next 15-16 hours. For someone who has just had a heart attack, troponin levels are bound to stay high for a couple of weeks. Thus, this test can help the cardiologists zero in on the most suitable treatment option. If the levels normalize within 12 hours from the time when one started experiencing chest pain, the chances of one having a heart attack are quite less. High levels must be taken as a warning sign for future heart problems. One must make certain lifestyle-related changes and seek medical advice to lower the risk of heart disease.

Reference Range for Troponin

Out of the three proteins that form the troponin complex, it is just the levels of TnI and TnT that are measured for those who are experiencing pain or heaviness in the chest region. Doctors can assess the extent of damage to the heart muscle by testing the levels of troponin after a heart attack. This test is definitely a useful tool for determining the extent of heart muscle damage. These are very helpful in the diagnosis of unstable angina or heart attack. If the level of TnI lies between 0-0.4 ng/mL and the level of TnT lies between 0-0.1 ng/mL, it is not a cause of serious concern. However, abnormally high levels are indicative of damage to the heart muscle. If a person is suffering from any medical condition that causes damage to the heart muscle, the levels of these proteins will rise above the normal range. The conditions that could cause raise the level of these proteins include certain kidney diseases, pulmonary hypertension, pulmonary embolism or trauma to the heart. Heart conditions such as myocarditis, supraventricular tachycardia or coronary artery spasm are other contributory factors. Certain medical procedures such as open heart surgery, cardiac angioplasty, electrical cardioversion or radiofrequency ablation of the heart could also cause elevate the levels of these proteins

Cardiologists can determine the condition of the heart of the patient by testing the levels of troponin. This provides them with useful prognostic information. Since persistently high levels of TnI and TnT are indicative of future health risks, people who have elevated levels must make changes to their lifestyle and follow the advice of their doctor to stay healthy.