From the Guidelines
The best interval for checking troponins is typically at presentation (baseline), 3 hours, and 6 hours after symptom onset in patients with suspected acute coronary syndrome. This approach is supported by the 2017 AHA/ACC clinical performance and quality measures for adults with ST-elevation and non-ST-elevation myocardial infarction, which recommends serial cardiac troponin I or T levels at presentation and 3 to 6 hours after symptom onset to identify a rising and/or falling pattern of values 1.
Key Considerations
- For high-sensitivity troponin assays, a 0-hour and 1-hour or 0-hour and 2-hour protocol may be sufficient.
- In patients with a low-to-intermediate risk of acute coronary syndrome, two negative troponin results 3 hours apart can effectively rule out myocardial infarction.
- For patients with initially negative troponins but ongoing symptoms or high clinical suspicion, additional measurements at 6-12 hours may be warranted, as recommended by the 2014 AHA/ACC guideline for the management of patients with non-ST-elevation acute coronary syndromes 1.
- The timing of troponin checks is crucial because troponin levels begin to rise 3-4 hours after myocardial injury, peak at 24-48 hours, and may remain elevated for 7-14 days.
Clinical Implications
- This serial testing approach helps clinicians distinguish between acute myocardial injury and chronic elevation, which is crucial for appropriate diagnosis and management of patients with chest pain or other symptoms suggestive of cardiac ischemia.
- The guidelines emphasize the importance of considering the time of symptom onset, or the time of presentation if symptom onset is ambiguous, when assessing troponin values 1.
From the Research
Interval to Check Troponins
- The optimal interval to check troponins is not explicitly stated in the provided studies, but study 2 suggests that repeat measurements of high-sensitivity cardiac troponin I (hs-cTnI) over hours can identify individuals with acute heart failure without acute coronary syndrome at risk for short- and long-term outcomes.
- In study 2, hs-cTnI was measured ≤12 hours from admission and repeated ≤6 hours thereafter, with a median interval of 3.4±1 hours between measurements.
- The study found that both individual measurements and the change (Δ) in hs-cTnI levels were associated with long-term outcomes, but the second measurement was more strongly associated with short-term outcomes.
- Studies 3, 4, 5, and 6 do not provide direct evidence on the optimal interval to check troponins, but they discuss the importance of troponin measurements in diagnosing and managing acute coronary syndrome and heart failure.
Troponin Measurement Frequency
- Study 2 suggests that measuring troponins at least twice, with an interval of ≤6 hours, may be beneficial in identifying patients at risk for short- and long-term outcomes.
- However, the exact frequency of troponin measurements is not specified in the provided studies, and further research is needed to determine the optimal measurement interval.
- It is essential to consider the clinical context and individual patient characteristics when determining the frequency of troponin measurements, as recommended by studies 3, 4, 5, and 6.