What are the American College of Emergency Physicians (ACEP) recommended testing strategies for cardiac markers?

Updated: Jul 30, 2021
  • Author: Kamal (Komo) Gursahani, MD, MBA; Chief Editor: Barry E Brenner, MD, PhD, FACEP  more...
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In patients with definite or possible acute coronary syndrome (ACS), in addition to clinical tools such as risk stratification scores (eg, the HEART score [history, electrocardiogram (ECG), age, risk factors, initial troponin]), [55] the serial evaluation of cardiac markers is essential to diagnosing acute myocardial infarction (MI) as well as for risk stratification for major adverse cardiac events (MACE). Most contemporary clinical practice guidelines use the cardiac troponin (cTn), whether conventional or high sensitivity (hs), exclusively for these purposes. The main clinical outcome of interest after initial emergency department (ED) evaluation of patients with suspected ACS is 30-day MACE. MACE includes MI, death, target lesion revascularization, or death.

In 2018, The American College of Emergency Physicians (ACEP) updated its level C recommendations regarding testing strategies for ruling out non-ST-elevation MI (NSTEMI) in lower risk patients to include the use of the HEART score and conventional or high-sensitivity cardiac troponins (hs-cTn) as follows:

  • In adult patients with suspected acute non–ST-elevation ACS, conventional troponin testing at 0 and 3 hours among low-risk patients with ACS (defined by HEART score 0 to 3) can predict an acceptable low rate of 30-day MACE.
  • A single high-sensitivity troponin result below the level of detection on arrival to the ED, or negative serial high-sensitivity troponin result at 0 and 2 hours is predictive of a low rate of MACE.
  • In adult patients with suspected acute non–ST-elevation ACS who are determined to be low risk based on validated accelerated diagnostic pathways that include a nonischemic ECG result and negative serial high-sensitivity troponin testing results both at presentation and at 2 hours can predict a low rate of 30-day MACE, allowing for an accelerated discharge pathway from the ED.

A 2021 prospective, multicenter study comprising 1452 patients suggests that a HEART score without the troponin measurement (ie, HEAR score) of less than 2 is a safe and reliable workup strategy to exclude NSTEMI, with a very low risk of MACE at 45 days. [56] Furthermore, a two-step HEART strategy combining the HEAR and HEART scores is potentially safe and could significantly lower the need for measuring troponin levels in very low-risk patients (HEAR score < 2; HEART score < 4) who present to the ED with chest pain.

The American Heart Association and American College of Cardiology (AHA/ACC) 2014 guideline for the management of ACS/NSTEMI recommends that cardiac troponin (I or T) be measured at presentation and 3-6 hours after symptom onset in all patients in which there is clinical suspicion. [4] Additional troponin measurements are indicated beyond 6 hours in patients with an initial normal serial troponin value and ischemic ECG findings and/or intermediate/high-risk clinical features. Timing of presentation and time of onset of symptoms should be considered when interpreting the troponin values. Finally, the guidelines state that creatine kinase (CK)-MB and myoglobin are not useful for the diagnosis of ACS. All of the above recommendations are cited with level A evidence. [4]

Few studies on the "time to positivity" have been performed, but serial samples that become positive in the 12- to 24-hour window are considered unlikely, unless the patient has ongoing symptoms of ischemia after admission. Although acute MI can therefore be ruled out in patients with negative serial marker results through the 6- to 9-hour period after presentation regardless of clinical suspicion, MACE is another consideration for higher risk patients.

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