What are Troponin I (Trop I) and Troponin T (Trop T)?

From the Guidelines

Troponin I (TnI) and Troponin T (TnT) are both effective biomarkers for detecting heart muscle damage, with Troponin I being highly specific to cardiac muscle and Troponin T having cardiac-specific isoforms that modern assays can distinguish from skeletal muscle variants 1. When interpreting troponin results, it's essential to consider the clinical context and potential false positives. The 2014 AHA/ACC guideline recommends using the 99th percentile of the upper reference level as the cutpoint for considering myocardial necrosis, and determining serial changes in troponin values to diagnose acute myocardial necrosis 1. Some key points to consider when using troponin assays include:

• Elevated levels typically appear 3-4 hours after cardiac injury, peak at 24-48 hours, and may remain elevated for 7-14 days 1
• Serial measurements showing a rise and/or fall pattern are more specific for acute myocardial injury than a single elevated value 1
• Troponin can also be elevated in conditions other than heart attacks, including heart failure, myocarditis, pulmonary embolism, sepsis, and renal failure 1
• Absolute changes in nanograms per liter of high-sensitivity cardiac troponin T levels appear to have a significantly higher diagnostic accuracy for AMI than relative changes 1 In clinical practice, either Troponin I or Troponin T can be used effectively, with most hospitals standardizing on one type. However, it's crucial to be aware of the sensitivity of the tests used for troponin evaluation and the cutpoint concentrations for clinical decisions 1. The diagnosis of NSTEMI requires cardiac troponin values to manifest an acute pattern consistent with the clinical events, including ischemic symptoms and electrocardiographic changes 1. Overall, troponin assays are valuable diagnostic tools for identifying myocardial infarction, but require careful interpretation in the clinical context.

From the Research

Trop I and Trop T Overview

• Troponin I and T are highly sensitive and specific markers for acute myocardial infarction (AMI) 2
• They are integral components of the evaluation for acute coronary syndrome (ACS) and occlusion myocardial infarction (OMI) 3
• Troponin elevation is a reflection of myocardial injury, and many conditions associated with critical illness may result in troponin elevation, including cardiac and non-cardiac conditions 3

Clinical Significance

• Elevated troponin levels are associated with increased rates of mortality, regardless of the underlying cause 4
• The maximum troponin level is a more sensitive and specific predictor of mortality and AMI than the initial or change in troponin level 4
• Troponin elevation can be caused by various conditions, including heart failure, dysrhythmia, dissection, pulmonary embolism, sepsis, and stroke 3, 5

Diagnostic Considerations

• Clinicians should consider the clinical context, patient symptoms, electrocardiogram, and ultrasound in their assessment of the patient with troponin elevation 3
• The accurate interpretation of raised cardiac troponin is challenging and relies on understanding the pathophysiologic mechanism leading to the release of cardiac biomarkers in the bloodstream 5
• Identifying potential confounding factors, both cardiac and non-cardiac in etiology, is crucial to understanding the clinical significance of elevated serum levels and identifying the best management strategy 5

Management

• Aspirin and dual antiplatelet therapy are recommended for patients with suspected acute coronary syndrome (ACS) unless contraindicated 6
• Parenteral anticoagulation, proton pump inhibitors, statins, angiotensin-converting enzyme inhibitors, beta blockers, nitroglycerin, and morphine may also be used in the management of ACS 6
• Percutaneous coronary intervention (PCI) with stent placement is recommended for patients with ST-segment elevation myocardial infarction, while fibrinolytic therapy may be used if PCI is delayed 6