Troponin is a muscle protein that is released into the bloodstream after myocardial injury of infarction. Troponin is the most specific biomarker of cardiac muscle injury. Usually, the two subtypes of troponin known as cardiac-specific troponin T (cTnT) and cardiac-specific troponin I (cTnI) are very low in the bloodstream. The normal cTnT levels is <0.1 ng/mL while the normal cTnI level is <0.5 ng/mL. Elevated levels of troponin indicate myocardial damage.
The onset of elevated troponin levels is 1 hour. Increased levels of cTnT and cTnI may be detected within 4-6 hours of myocardial injury. High-sensitivity troponin assays may help detect myocardial damage early. Since increased troponin levels are associated with increased risk of mortality, patients with elevated troponin levels should be treated aggressively.
The peak of increasing levels of troponin is within 10-24 hours.
After myocardial injury, troponin levels return to baseline within 5-14 days. Compared with other cardiac enzymes, troponin levels take the longest time to return to normal.
Troponin is the most specific indicator for cardiac muscle damage. The muscle protein has a high specificity and sensitivity for myocardial muscle injury. Other cardiac enzymes that are less specific than troponin include myoglobin and creatine kinase CK-MB (refer to the Picmonics on "Cardiac Enzyme Evaluation: Myoglobin" and "Cardiac Enzyme Evaluation: Creatine Kinase CK-MB").
Patients with elevated troponin levels should be treated aggressively to minimize complications. Rapid high-sensitivity troponin assays may be done at the bedside to determine protein levels. Since increased troponin levels are associated with a high risk of mortality, patients with low levels at the bedside or emergency department are also treated aggressively to minimize damage.
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