Troponin is a protein found within the muscle cells of your heart. When these heart muscle cells experience damage, they can release troponin into the bloodstream. Measuring troponin levels in the blood is a common diagnostic tool used to assess heart health.
What is Troponin
Troponin is a complex of three regulatory proteins involved in muscle contraction: troponin C, troponin I, and troponin T. While troponin C is found in both cardiac and skeletal muscle, troponin T and troponin I are specific to cardiac muscle cells. These cardiac-specific isoforms, often abbreviated as cTnT and cTnI, are the primary markers used in medical diagnostics.
Why Troponin Levels are Measured
Troponin is contained within the heart muscle cells and is released into the bloodstream when the heart muscle is damaged. This makes troponin a highly sensitive and specific marker for injury to the heart muscle. Its primary use is in the diagnosis of acute myocardial infarction, commonly known as a heart attack. In emergency settings, especially when patients present with chest pain, measuring troponin levels helps determine if heart damage has occurred.
Interpreting Troponin Test Results
Troponin levels are measured in nanograms per liter (ng/L) or nanograms per milliliter (ng/mL). In healthy individuals, troponin levels are extremely low, near zero or undetectable with conventional tests. Modern high-sensitivity troponin assays can detect even minute amounts, with normal ranges for high-sensitivity cardiac troponin I below 15 ng/L for women and 20 ng/L for men, and for high-sensitivity cardiac troponin T below 14 ng/L.
A specific number like “6” needs careful interpretation, as the unit of measurement is crucial (e.g., 6 ng/L is vastly different from 6 ng/mL). Each laboratory has its own specific cutoff or threshold value for what is considered an elevated or “positive” result. For example, a high-sensitivity cardiac troponin T level above 14 ng/L may indicate heart damage. Beyond a single measurement, doctors consider the trend of troponin levels, looking for a rise and/or fall over several hours, which is more indicative of acute injury than a single elevated reading.
Other Causes of Elevated Troponin
While a heart attack is the most common reason for elevated troponin levels, other conditions can also cause an increase in these proteins. Any condition that causes stress or damage to the heart muscle can lead to troponin release. Examples include severe heart failure, where damaged contractile proteins can leak into circulation.
Kidney disease can also result in elevated troponin levels, as decreased kidney function may reduce the clearance of troponin from the bloodstream. Other causes include pulmonary embolism, which can strain the right side of the heart, and severe infections like sepsis, where inflammation and oxygen supply-demand imbalances can damage heart muscle. Myocarditis, inflammation of the heart muscle, and even strenuous physical exertion can also lead to transient troponin elevations.
What Happens After a Troponin Test
After a troponin test, the next steps depend on the results and the patient’s overall clinical picture. If the initial troponin level is normal, but symptoms persist, repeat testing occurs within 3 to 12 hours, because it can take a few hours for levels to rise after the onset of heart damage. If troponin levels are elevated, further diagnostic tests are performed.
These additional tests may include an electrocardiogram (ECG) to assess the heart’s electrical activity, or an echocardiogram to visualize heart structure and function. Depending on the findings, a stress test or even a coronary angiogram might be considered to evaluate blood flow to the heart. Medical professionals combine the troponin results with the patient’s symptoms, medical history, and other diagnostic findings to form a comprehensive diagnosis and determine the appropriate treatment plan.