In June 2018, the ACEP Board of Directors approved a clinical policy on the evaluation and management of adult patients presenting with suspected non–ST-elevation acute coronary syndrome (NSTE ACS).¹ In its complete form, this policy can be found on the ACEP website .

Emergency physicians routinely rule out ACS in patients presenting with chest pain and have become very good at targeting timely interventions in the obvious cases of ST-elevation myocardial infarction but still miss up to 2 percent of acute myocardial infarctions, particularly those with non–ST-elevation myocardial infarction (NSTEMI). The purpose of this policy was to focus on the initial diagnosis and treatment of patients who present with potential NSTE ACS.

In developing the policy, the ultimate outcome measure was the 30-day incidence of major adverse cardiovascular event (MACE). This includes cardiovascular death and myocardial infarction, as well as what some argue is more subjective in terms of actual need, coronary revascularization. Most emergency physicians strive to attain a miss rate of less than 1 percent. However, it is questionable if the benefits of further testing outweigh the risks of harm of untreated disease once that threshold reaches 2 percent, which the committee felt was a more realistic expectation. With shared decision making, patients may be willing to accept rates higher than those to which physicians hold themselves accountable.

Emergency departments are so often congested with patients awaiting serial testing (laboratory and noninvasive) to rule out potential ACS that entire units have been dedicated to observing these patients, yet there is questionable benefit. Researchers have been looking for diagnostic strategies, single or serial troponins, and ECGs to try to identify at-risk patients sooner and expedite their transition of care. One strategy adopted internationally and slowly taking hold in the United States is the advent of high-sensitivity troponins. Although these have great promise for detecting potential disease sooner, without proper protocols, they can lead to excessive false positives. Regardless, their use holds great promise in expediting the care of patients suspected of NSTE ACS.

Ultimately, the purpose of this policy was to help ED clinicians expedite the care of patients presenting with chest pain who are at risk for NSTE ACS. The first three questions focus on initial identification of patients at low risk for MACE, using history and limited testing. Are there patients with suspected ACS who are safe to discharge based on initial risk stratification? Do serial troponins really help, and how long do we have to wait to do that second troponin? Does getting early non-invasive diagnostic testing for ACS prior to discharge from the emergency department really help decrease MACE rates? The goal was to see if there were strategies to expedite the initial evaluation and discharge of these patients without resorting to prolonged ED stays (four to six hours or longer) while still limiting the number of 30-day MACE.

The fourth and last question looks at the role of early antiplatelet therapy in patients with acute NSTEMI and focuses on timing. Because of early literature and general consensus on the accepted use of heparin and enoxaparin, the literature search and recommendations targeted newer oral antiplatelet agents. The goal was to ensure emergency physicians were not held accountable for timely administration of such agents if such delays were not associated with worse outcomes.

For each critical question, a structured literature review was performed, evidence was systematically graded (see Table 1), and evidence-based recommendations were presented.

Critical Questions

1. In adult patients without evidence of ST-elevation ACS, can initial risk stratification be used to predict a low rate of 30-day MACE?

Patient Management Recommendations

• Level A recommendations. None specified.
• Level B recommendations. In adult patients without evidence of ST-elevation ACS, the history, ECG, age, risk factors, and troponin (HEART) score can be used as a clinical prediction instrument for risk stratification. A low score (≤3) predicts 30-day MACE miss rate within a range of 0 to 2 percent.
• Level C recommendations. In adult patients without evidence of ST-elevation ACS, other risk-stratification tools, such as thrombolysis in myocardial infarction (TIMI), can be used to predict the rate of 30-day MACE.

2. In adult patients with suspected acute NSTE ACS, can troponin testing within three hours of ED presentation be used to predict a low rate of 30-day MACE?

Patient Management Recommendations

• Level A recommendations. None specified.
• Level B recommendations. None specified.
• Level C recommendations.
  1. In adult patients with suspected acute NSTE ACS, conventional troponin testing at 0 and 3 hours among low-risk ACS patients (defined by HEART score 0 to 3) can predict an acceptable low rate of 30-day MACE.
  2. A single high-sensitivity troponin result below the level of detection on arrival to the emergency department or negative serial high-sensitivity troponin results at 0 and 2 hours are predictive of a low rate of 30-day MACE.
  3. In adult patients with suspected acute NSTE 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 emergency department.

3. In adult patients with suspected NSTE ACS in whom acute myocardial infarction has been excluded, does further diagnostic testing (eg, provocative, stress test, computed tomography [CT] angiography) for ACS prior to discharge reduce 30-day MACE?

Patient Management Recommendations

• Level A recommendations. None specified.
• Level B recommendations. Do not routinely use further diagnostic testing (CT coronary angiography, stress testing, myocardial perfusion imaging) prior to discharge in low-risk patients in whom acute myocardial infarction has been ruled out to reduce 30-day MACE.
• Level C recommendations. Arrange follow-up in one to two weeks for low-risk patients in whom myocardial infarction has been ruled out. If no follow-up is available, consider further testing or observation prior to discharge (consensus).

4. Should adult patients with acute NSTEMI receive immediate antiplatelet therapy in addition to aspirin to reduce 30-day MACE?

Patient Management Recommendations

• Level A recommendations. None specified.
• Level B recommendations. None specified.
• Level C recommendations. P2Y12 inhibitors and glycoprotein IIb/IIIa inhibitors may be given in the emergency department or delayed until cardiac catheterization.

In conclusion, patients who present with chest pain with low risk for ACS (eg, HEART score ≤3) and a normal troponin at 0 and 3 hours post-presentation may be discharged safely, with less than a 2 percent risk of subsequent 30-day MACE. The advent of high-sensitivity troponins will help accelerate this rule-out protocol. In such low-risk cases, we could find no data to support subsequent noninvasive testing. Our ultimate goal should be to prevent harm from missing MACE, but also from overtesting patients. Finally, our last question confirms that it is acceptable to delay further antiplatelet therapy, beyond heparin, especially if there are concerns over potential adverse bleeding or competing priorities.

Dr. Tomaszewski is professor of clinical emergency medicine at the University of California San Diego Health and chief medical officer of El Centro Regional Medical Center.

Reference

1. Tomaszewski CA, Nestler D, Shah KH, et al. American College of Emergency Physicians. Clinical policy: critical issues in the evaluation and management of emergency department patients with suspected non–ST-elevation acute coronary syndromes. Ann Emerg Med. 2018;72(5):e65-e106.