Troponin is a protein found within the muscle cells of the heart. It is a complex of three subunits: troponin C, troponin I, and troponin T, all of which play a role in muscle contraction and relaxation. In a healthy individual, troponin is typically present in the bloodstream at very low or undetectable levels. When heart muscle cells are damaged, troponin is released into the blood, making it a reliable indicator of heart injury.
The Troponin Test Explained
Doctors often order a troponin test to determine if a patient’s symptoms are related to a heart problem. Symptoms suggesting a heart attack include chest pain, shortness of breath, discomfort radiating to the arms, neck, or jaw, sudden fatigue, dizziness, nausea, or excessive sweating. The procedure involves drawing a small blood sample from a vein, usually in the arm, which is then analyzed in a laboratory.
A single troponin measurement may not be sufficient for diagnosis. Healthcare providers often conduct a series of tests over time to observe the trend of troponin levels. A rising or falling pattern in these serial measurements, rather than just one isolated number, helps clinicians determine the presence and extent of heart muscle damage. This approach allows for earlier detection of heart injury and helps guide prompt medical decisions.
Normal and High Troponin Levels
The specific reference ranges for troponin can vary slightly between different laboratories and the type of test used. Modern high-sensitivity troponin tests (hs-cTn) are widely used because they can detect even very small amounts of troponin earlier. For high-sensitivity cardiac troponin T (hs-cTnT), a level below 14 ng/L is generally considered normal. For high-sensitivity troponin I (hs-cTnI), normal levels are typically below 26 ng/L.
Even small increases above the normal range can indicate some degree of cardiac damage. A level above the 99th percentile of a healthy population is generally considered elevated. For instance, a high-sensitivity cardiac troponin T level exceeding 14 ng/L suggests possible heart damage or a heart attack. A diagnosis of a heart attack usually requires a significant rise or fall in troponin levels over serial measurements, combined with the patient’s symptoms and other diagnostic findings.
Levels that are moderately elevated may be considered borderline or indeterminate, often prompting further monitoring and repeat testing to see if the numbers are trending upward. A level of 0.40 ng/mL or more can be a strong indication of a heart attack. The interpretation of troponin results is always done in the context of the patient’s full clinical picture.
Causes of Elevated Troponin
The most common and urgent reason for significantly elevated troponin levels is a myocardial infarction, commonly known as a heart attack. This occurs when blood flow to the heart muscle is blocked, causing damage to heart cells. However, troponin can become elevated due to various other cardiac and non-cardiac conditions.
Other cardiac conditions that can lead to increased troponin include myocarditis (inflammation of the heart muscle), severe heart failure, stress cardiomyopathy, atrial fibrillation, or prolonged strenuous exercise. Non-cardiac causes for elevated troponin levels include chronic kidney disease, pulmonary embolism (a blood clot in the lungs), severe infections like sepsis, and certain medical procedures like cardioversion or heart surgery.
A healthcare professional interprets the troponin result alongside symptoms, medical history, and other diagnostic tests, such as an electrocardiogram, to pinpoint the exact cause of the elevation.