What are the guidelines for troponin (cardiac biomarker) level measurement and treatment in patients with suspected acute coronary syndrome?

From the Guidelines

Troponin measurement is essential for diagnosing acute coronary syndrome (ACS), with testing recommended at presentation and 3-6 hours later, as stated in the 2017 AHA/ACC guideline 1.

Key Points for Troponin Kinetics

• High-sensitivity troponin assays can detect myocardial injury earlier, with values above the 99th percentile upper reference limit considered abnormal.
• A significant rise or fall in troponin levels (typically >20% change) with at least one value above the 99th percentile indicates acute myocardial injury.
• For patients with confirmed ACS, immediate treatment includes dual antiplatelet therapy with aspirin plus a P2Y12 inhibitor such as ticagrelor or clopidogrel, as recommended by the 2014 AHA/ACC guideline 1.
• Anticoagulation with heparin or low molecular weight heparin should be initiated, and additional treatments include high-intensity statins, beta-blockers, and ACE inhibitors or ARBs for most patients.
• Patients with ST-elevation myocardial infarction require immediate reperfusion therapy, preferably primary percutaneous coronary intervention within 90 minutes of first medical contact, or fibrinolytic therapy if PCI is not available within 120 minutes, as stated in the 2015 international consensus on cardiopulmonary resuscitation and emergency cardiovascular care science with treatment recommendations 1.

Interpretation of Troponin Elevation

• Troponin elevation must be interpreted in clinical context, as non-ACS conditions like heart failure, pulmonary embolism, and renal failure can also cause elevated levels.
• Serial measurements showing a characteristic rise and fall pattern help distinguish acute from chronic elevations.
• The use of troponins at 0 and 2 hours as a stand-alone measure for excluding the diagnosis of ACS is strongly discouraged, as recommended by the 2015 international consensus on cardiopulmonary resuscitation and emergency cardiovascular care science with treatment recommendations 1.

Clinical Recommendations

• Serial cardiac troponin I or T levels should be obtained at presentation and 3 to 6 hours after symptom onset in all patients who present with symptoms consistent with ACS to identify a rising and/or falling pattern of values 1.
• Additional troponin levels should be obtained beyond 6 hours after symptom onset in patients with normal troponin levels on serial examination when changes on ECG and/or clinical presentation confer an intermediate or high index of suspicion for ACS, as recommended by the 2014 AHA/ACC guideline 1.

From the Research

Troponin Kinetics and Measurement Guidelines

• The measurement of troponin levels is crucial in diagnosing acute coronary syndrome (ACS) and guiding treatment decisions 2, 3, 4.
• High-sensitivity cardiac troponin I assays can detect even small cardiac damage, making them useful for identifying low-risk patients who can be discharged from the hospital 2.
• A troponin concentration of less than 5 ng/L has a negative predictive value of 99.6% for index myocardial infarction or subsequent myocardial infarction or cardiac death at 30 days 2.

Treatment and Risk Assessment

• Patients with suspected ACS and troponin concentrations of 0.05 to 0.19 ng/mL are at high risk of recurrent myocardial infarction and death, and lowering the diagnostic threshold to 0.05 ng/mL can improve clinical outcomes 4.
• A 2-hour troponin test can be safe and effective in evaluating high-risk patients with suspected ACS, with a negative predictive value of 98.7% for 30-day myocardial infarction, death, cardiac arrest, or dysrhythmia 5.
• Elevated troponin levels can be caused by various diseases, such as sepsis, hypovolemia, atrial fibrillation, and renal failure, and should be targeted accordingly 6.

Clinical Implications

• Troponin kinetics and measurement guidelines can help identify patients at low risk of cardiac events who can be discharged from the hospital, reducing hospital admissions and healthcare costs 2.
• The use of high-sensitivity troponin assays and 2-hour troponin tests can improve the diagnosis and treatment of patients with suspected ACS, reducing morbidity and mortality 4, 5.
• Clinicians should consider alternative causes of elevated troponin levels and target the underlying cause, rather than treating with antithrombotic and antiplatelet agents 6.