Troponin

Clinical significance and laboratory diagnostics

Measurement of blood cardiac troponins is recommended for all patients with suspected non-ST-elevation acute coronary syndrome. The purpose of the test is to confirm or rule out myocardial infarction and to assess the risk of adverse outcomes.

• Diagnostic threshold — an increase in marker concentration above the 99th percentile of the upper reference limit.
• Time standards — laboratory results must be obtained within 60 minutes of blood collection. If laboratory testing is unavailable, qualitative or semi-quantitative point-of-care tests are used. The future implementation of high-sensitivity Point of Care tests is anticipated.
• Marker comparison — cardiac troponins are a more sensitive and specific method compared to the MB fraction of creatine kinase and myoglobin; myoglobin is not recommended for clinical use.
• Management with normal values — if initial troponin levels are normal but clinical suspicion of ACS persists, repeat testing must be scheduled at a later time: 3 hours or later. This is particularly important when using less sensitive assays.

How to interpret changes in troponin levels?

The biomarker concentration rises to diagnostically significant levels 1–6 hours after the ischemic episode. To confirm acute myocardial injury, repeat testing is required to assess the dynamics—an increase and/or decrease in the parameter.

• Acute myocardial infarction — diagnosed in the presence of acute myocardial ischemia accompanied by troponin dynamics. If there was no baseline elevation, a rise and/or fall in concentration above the 99th percentile of the upper reference limit is recorded. If levels were stably elevated with variability of no more than 20%, the criterion is a concentration increase of more than 20% from baseline. Type 1 infarction (atherosclerosis and thrombosis) and Type 2 infarction (supply-demand mismatch of myocardial oxygen) are distinguished.
• Acute myocardial injury — diagnosed when troponin levels show dynamics without signs of acute myocardial ischemia. The cause may be ischemic, non-ischemic, or related to extracardiac factors.
• Chronic myocardial injury — diagnosed when troponin levels are persistently elevated and remain unchanged. Potential causes include structural heart disease, chronic kidney disease, etc.

Causes of non-ischemic elevation

Acute elevations in cardiac troponins are observed not only in Type 1 myocardial infarction associated with atherothrombosis, but also in non-atherothrombotic pathogenetic variants of infarction, as well as in acute non-ischemic myocardial injury.

• Heart failure — acute and chronic. In acute decompensated heart failure, troponin levels are elevated almost universally, which complicates the diagnosis of acute myocardial infarction and does not always indicate its presence.
• Cardiovascular pathologies — pulmonary embolism, myocarditis, cardiomyopathies, acute aortic syndrome.
• Extracardiac factors — sepsis, acute cerebrovascular accident, poisonings.
• Renal dysfunction — troponin elevation is frequently associated with non-ischemic injury and indicates a high risk of cardiac complications. Chronic kidney disease can be a cause of chronic myocardial injury.

Role in hypertrophic cardiomyopathy

Measurement of highly specific cardiac troponin is not part of the routine evaluation for patients with hypertrophic cardiomyopathy. Elevated troponin levels are associated with:

• Severity of left ventricular hypertrophy.
• Severity of diastolic dysfunction.
• Severity of functional impairment, including myocardial ischemia and progression of chronic heart failure.

Class and exam questions

What else to study on this topic

• Acute Coronary Syndrome (ACS)
• Type 1 and Type 2 Myocardial Infarction
• Acute Decompensated Heart Failure
• Creatine Kinase (CK-MB)

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.