Version July 2025
INTRODUCTION —
Chest pain accounts for approximately eight million annual visits to emergency departments (EDs) in the United States [1]. Acute coronary syndrome (ACS) evaluations account for approximately 10 to 20 percent of all these cases. The management of this group of patients is challenging due to the large number of patients presenting with chest symptoms and the need to efficiently and safely manage such patients [2].
This topic discusses the evaluation of patients suspected of having a non-ST-elevation ACS (NSTEACS).
The approach to patients with chest pain or chest discomfort is discussed separately. (See "Approach to the adult with nontraumatic chest pain in the emergency department" and "Initial evaluation and management of suspected acute coronary syndrome (myocardial infarction, unstable angina) in the emergency department".)
The approach to management of ST-elevation myocardial infarction (STEMI) and other aspects of NSTEACS management are presented separately. (See "Overview of the acute management of ST-elevation myocardial infarction" and "Overview of the acute management of non-ST-elevation acute coronary syndromes".)
Information on specific aspects of troponin testing, including high-sensitivity assays, sex-specific cutoffs, and chronic troponin elevation, is discussed separately. (See "Troponin testing: Clinical use".)
DEFINITION OF ACUTE CORONARY SYNDROME —
The term "ACS" is applied to patients in whom there is evidence or suspicion of myocardial ischemia or infarction. There are three types of ACS:
●STEMI and NSTEMI – ST-elevation MI (STEMI) and non-ST-elevation MI (NSTEMI) are characterized by a typical rise or fall in serum troponin [3]. (See "Diagnosis of acute myocardial infarction", section on 'Joint Task Force definitions'.)
●Unstable angina – Unstable angina (UA) is characterized by suspicion for new or worsening myocardial ischemia in the absence of elevated biomarkers and is often a clinical diagnosis based on history, dynamic electrocardiogram (ECG) changes, or inducible ischemia on stress testing. The use of highly sensitive troponin assays has reduced the proportion of patients diagnosed with UA; these assays detect low levels of myocardial injury consistent with the diagnosis of NSTEMI [4].
GOALS OF EVALUATION —
The primary focus of the initial evaluation of patients with possible ACS is to reasonably confirm or exclude the presence of ACS in an expeditious manner. With a provisional diagnosis of STEMI, immediate therapy should begin. In the absence of STEMI, the diagnostic assessment for NSTEACS and other causes of chest symptoms continues until NSTEMI or UA are either diagnosed or reasonably excluded. ACS is reasonably excluded if the 30-day risk of death or ACS is less than 1 or 2 percent, which correlates with negative predictive value and sensitivity of more than 98 or 99 percent [5-9].
For patients with evidence of MI or suspected ACS, appropriate management strategies should be initiated, as discussed elsewhere. (See "Initial evaluation and management of suspected acute coronary syndrome (myocardial infarction, unstable angina) in the emergency department", section on 'Management'.)
INITIAL EVALUATION
Tests — The initial tests obtained for evaluation of NSTEACS include:
●Electrocardiography – Clinicians should obtain a 12-lead ECG within 10 minutes of arrival and continuous ECG monitoring. (See "Initial evaluation and management of suspected acute coronary syndrome (myocardial infarction, unstable angina) in the emergency department", section on 'Electrocardiogram assessment'.)
●History and examination – Clinicians should obtain a brief history and physical examination. The history should include questions that evaluate whether the chest pain is likely to represent myocardial ischemia. (See "Initial evaluation and management of suspected acute coronary syndrome (myocardial infarction, unstable angina) in the emergency department", section on 'History' and "Initial evaluation and management of suspected acute coronary syndrome (myocardial infarction, unstable angina) in the emergency department", section on 'Examination findings'.)
●Laboratory tests – Clinicians should obtain a high-sensitivity or sensitive cardiac troponin assay, serum electrolytes, serum creatinine, and a complete blood count. (See "Initial evaluation and management of suspected acute coronary syndrome (myocardial infarction, unstable angina) in the emergency department", section on 'Cardiac biomarkers and other laboratory testing'.)
●Chest radiography – Patients with suspected ACS should have a chest radiograph to evaluate for other causes of chest discomfort, including heart failure, pneumonia, aortic dissection, pneumothorax, or large pericardial effusion [10].
Initial integrated risk assessment (HEART Score) — In patients with suspected NSTEACS, we suggest calculating the modified HEART Score, which includes all components of the original HEART Score except points for troponin values. Troponin values are factored in separately. The modified HEART score includes:
●History – If suspicion for ACS based on history is high, 2 points; if suspicion is moderate, 1 point; otherwise, 0 points. For the HEART Score, high suspicion is defined by the presence of symptoms usually characterized as "typical." These symptoms require a location that is central or left-sided chest pain with or without radiation to the arms or throat, characteristics of heaviness, squeezing, radiation to the arms or throat, and associated diaphoresis or clamminess. Patients with typical and atypical features are classified as moderate. In patients with atypical symptoms only, without chest pain, or with right-sided pain, the patient receives 0 points (ie, "atypical" chest pain).
●ECG – If the ECG shows ST-segment depression, 2 points; if nonspecific changes are present, 1 point; otherwise, 0 points. ST-segment depression requires the presence of presumably new horizontal or downsloping ST depression of at least ≥1 mm in two contiguous leads or >1 mm T-wave inversion in two contiguous leads. Nonspecific changes include other ECG findings (T-wave flattening) or indeterminate findings (eg, paced rhythm, presence of bundle branch block).
●Age – If age is ≥65 years, 2 points; 45 to 64 years, 1 point; otherwise, 0 points.
●Risk factors – If the patient has ≥3 atherosclerotic risk factors, 2 points; if 1 or 2 risk factors, 1 point; otherwise, 0 points. Atherosclerotic risk factors include hypertension, body mass index >30 kg/m2, current or prior tobacco use, diabetes mellitus, family history of coronary artery disease (CAD) in a first-degree relative, and hypercholesterolemia.
More information on the modified HEART Score is presented below. (See 'HEART Score ≥4 points' below and 'High-sensitivity troponin HEART Pathway' below and 'Modified HEART Pathway' below.)
Another score, Emergency Department Assessment of Chest Pain Score (EDACS), has sensitivity that ranges from 88 to 100 percent and is not as well-studied as the HEART score [11,12]. When compared in the same cohort of 5799 patients in the United States, EDACS had a 1 percent rate of major adverse cardiac events versus the HEART Pathway's 0.4 percent rate [13].
MANAGEMENT AFTER INITIAL TESTING
Approach in high-risk patients — High-risk patients with suspected NTEACS include the following:
Ischemic ECG changes — Patients with ST-depression ≥1 mm in two contiguous leads or T-wave inversion in a pattern consistent with ischemia should be observed in the hospital for management of suspected NSTEMI. In such patients, the approach to management may be further guided by the pattern of ECG changes (eg, resolution, worsening) and by troponin values. (See "Non-ST-elevation acute coronary syndromes: Selecting a management strategy", section on 'Evidence of infarction (NSTEMI)'.)
Known coronary artery disease — In patients with a history of CAD (eg, prior MI, prior stenting or coronary artery bypass graft surgery, ≥70 percent obstruction on prior imaging) who have a history suspicious for NSTEACS but no ECG evidence of ischemia, additional evaluation for CAD is typically required. (See 'Indeterminate testing or elevated risk' below.)
HEART Score ≥4 points — In patients in whom there is a high clinical suspicion for ACS based on symptoms and risk factors, it is most appropriate to obtain troponin values at time zero and at two hours for a high-sensitivity cardiac troponin (hs-cTn) assay and zero and three hours for a conventional cTn assay. If troponin testing does not resolve the high clinical suspicion for ACS, additional troponin values (ie, at six hours) or prolonged observation with or without a stress or anatomic test for obstructive CAD are reasonable options. (See 'Indeterminate testing or elevated risk' below.)
Approaches in lower-risk patients — For most patients with suspected NSTEACS who present within 3 to 12 hours after symptom onset and who have no history of CAD and either a normal ECG or nonspecific ECG changes, we suggest evaluation with a structured diagnostic protocol rather than with a less structured approach to evaluation (eg, serial troponins, clinical gestalt). In patients with other presentations (eg, within one hour of symptom onset) and in certain scenarios (eg, persistent troponin elevation), particular protocols or alternative means of evaluation may be required. (See 'Special circumstances' below.)
Each protocol has advantages and disadvantages relative to other protocols [14]. Often, the choice of protocol depends on the type of troponin assay (highly sensitive or sensitive) and which results of troponin testing (eg, limit of detection reporting or normal/abnormal results only) are available to the clinician.
High-sensitivity troponin HEART Pathway — At centers in which highly sensitive assays are available and troponin assay results are reported at values close to the lower limit of quantitation or detection, the high-sensitivity HEART Pathway can be used. In this pathway, the first steps of the evaluation are to obtain the necessary components of the modified HEART score and an initial troponin value. (See 'Initial evaluation' above.)
In patients with known CAD, ischemic ECG findings, or a modified HEART Score ≥4 points, management often includes additional testing, as described elsewhere in this topic. (See 'Known coronary artery disease' above and 'Ischemic ECG changes' above and 'HEART Score ≥4 points' above.)
The approach to management of lower-risk patients with a HEART Score 0 to 3 points depends on the initial troponin value:
●First troponin value is very low – If the initial troponin value is very low (eg, near the limit of quantitation), the patient can be safely discharged without further testing. In a trial in which patients met these criteria, there was a low risk of death or MI at 30 days (0.2 percent) and high accuracy for exclusion of death or acute MI (sensitivity 99.7 percent, negative predictive value [NPV] 99.8 percent) [15].
●First troponin value not very low – If the first troponin is normal but not very low, obtain another troponin in two hours. If the two-hour troponin is lower than the 99th percentile value (ie, normal) for the troponin assay and has not increased appreciably compared with the first troponin, the patient can be discharged. The amount that the assay can increase depends on the assay. In a trial that used these criteria, patients who ruled out had a low risk of death or MI at 30 days (0.3 percent) and high accuracy for exclusion of death or acute MI (sensitivity 98.6 percent, NPV 99.7 percent) [15].
●First and second values fail to exclude ACS – If the patient does not rule out based on the criteria above, the patient requires additional evaluation. Additional evaluation typically includes another troponin value performed at six hours and additional testing (eg, stress imaging) based on clinical characteristics. (See 'Indeterminate testing or elevated risk' below.)
●Decreasing troponin values within normal limits – In low-risk patients who present soon after the onset of symptoms, we do not consider troponin values that are normal but decreasing evidence of MI [16]. In patients who present late (eg, >12 hours) after the onset of suspicious symptoms, troponin values that remain within normal limits but that are decreasing can occur. In such patients, management depends on an individualized assessment of factors that include ongoing symptoms, risk factors, and ECG changes, as well as the specific findings from troponin testing.
There is evidence that use of the high-sensitivity HEART Pathway reduces the risk of MI by a small amount compared with the modified HEART Pathway. In a trial of patients assigned to management with the high-sensitivity HEART Pathway or modified HEART Pathway, the rate of MI at 30 days was lower in the high-sensitivity group (6.2 versus 7 percent; difference 0.9 percent, 95% CI 0.3-1.5) and the rates of death were similar (0.9 percent) [15].
Studies that compared the high-sensitivity HEART Pathway and other pathways, which are few, are discussed elsewhere in this topic. (See 'Rationale' below.)
Modified HEART Pathway — The modified HEART Pathway uses the history, ECG, age, and risk factor components from the HEART score to create a risk score along with the results of sensitive troponin assays to determine the disposition of patients with suspected NSTEMI (algorithm 1). (See 'Initial integrated risk assessment (HEART Score)' above.)
In patients with a modified HEART score of 0 to 3 points, we obtain two sensitive troponin values at zero hours and three hours later. The management depends on the troponin values:
●Two normal troponin values – In patients with a HEART score of 0 to 3 and two appropriately timed and normal troponin values, the risk of ACS is very low. Further evaluation (eg, stress testing) for ACS is generally not indicated, and other causes of chest symptoms should be pursued. However, several caveats to this approach exist and are discussed elsewhere in this topic. (See 'Special circumstances' below.)
●Any elevated troponin value – In patients with a HEART score of 0 to 3 and a troponin value above the upper reference limit, the diagnosis of myocardial injury is confirmed and, in the presence of ACS symptoms and absence of chronic troponin elevation, the provisional diagnosis of NSTEMI is established. The approach to choosing a management strategy for the treatment of NSTEMI is presented separately. (See "Non-ST-elevation acute coronary syndromes: Selecting a management strategy".)
Conditions in which troponin may be chronically elevated include heart failure and chronic kidney disease. (See 'Conditions with chronic troponin elevation' below.)
●Increase in troponin values within normal limits – In patients whose second troponin value is normal but rises toward the boundary of the upper limit of normal, it is reasonable to obtain a third troponin value in another hour (ie, three hours after presentation).
●HEART score ≥4 points – Patients with a HEART score of ≥4 points should undergo management consistent with an elevated risk of ACS. (See 'HEART Score ≥4 points' above.)
Research that compares the modified HEART Pathway with the high-sensitivity HEART Pathway is discussed elsewhere in this topic [15]. (See 'High-sensitivity troponin HEART Pathway' above.)
Compared with evaluation without a specific pathway (ie, usual care with sequential troponin values), the relative effectiveness of the HEART Pathway varied between trials:
●Using mostly hs-cTn assays, a randomized trial compared the HEART Pathway approach with usual care [17]. This study allowed for discharge if a patient had a HEART score ≤3 points and either one or two negative troponin assays. If a patient was discharged after only one troponin value, a second troponin was obtained the same day or the next day. The combined rate of death, MI, any type of revascularization, any stenosis >50 percent, or unstable angina presentation within six weeks of enrollment was lower in the HEART Pathway group compared with the usual care group (18.9 versus 22.2 percent). Among patients with a HEART score ≤3 points, death, MI, or revascularization occurred in 1 percent. Time of observation in the ED and readmission rate were similar.
●Using sensitive troponin assays at zero and three hours, a randomized trial that compared the HEART Pathway approach with usual care found similar rates of death (none in either group) or MI (5 versus 6.4 percent) within 30 days of discharge [18]. For the HEART Pathway approach, the sensitivity was 100 percent (95% CI 63-100) and the NPV was 100 percent (95% CI 95-100) for the outcome of major adverse cardiac events at 30 days after discharge, while use of serial troponins had a sensitivity of 88 percent (95% CI 93-99) and an NPV of 99 percent (95% CI 96-100). Patients in the HEART Pathway group had decreased length of stay (9.9 versus 21.9 hours) and lower use of cardiac testing 30 days after discharge (56.7 versus 68.8 percent).
Other approaches — Other approaches to the evaluation of suspected NSTEACS have reasonable diagnostic accuracy but may be less accurate in common subgroups of patients (eg, known CAD), less accurate relative to other methods, or less well-studied:
●0/2-hour pathways – This approach is similar to the European Society of Cardiology (ESC) 0/1-hour algorithm; it requires a very low 0-hour troponin or both a low 0-hour troponin and a small change between the 0- and 2-hour troponin. Examples of this approach include a pathway used at one author's institution and the American College of Cardiology (ACC) Expert Consensus Pathway [19-21].
In a study of the ACC Expert Consensus Pathway, diagnostic accuracy was relatively low in patients with known CAD (NPV 98.5 percent) [21].
●Single troponin or "one and done" approach – Single troponin assay approaches have reasonable accuracy and are attractive for their simplicity and potential to rapidly exclude acute MI. However, this approach does not explicitly account for ECG changes or other clinical variables that are associated with a relatively high risk of outcomes. (See 'Known coronary artery disease' above and 'Ischemic ECG changes' above and 'High-sensitivity troponin HEART Pathway' above.)
The single troponin assay approach uses a highly sensitive troponin assay value obtained at presentation and reporting of troponin concentrations near the limit of detection or quantitation to exclude MI. In patients with a nonischemic ECG, the accuracy of this method increases by a small amount:
•In a study that included 1849 patients with suspected NSTEACS and adjudicated for acute MI, an initial hs-cTnI <6 ng/L had 100 percent sensitivity and specificity [22]. The prevalence of death or acute MI in this population was 0.9 percent.
•In a meta-analyses of studies that included patients with a single hs-cTn below the limit of detection of 5 ng/L and nonischemic ECG changes, the NPVs for MI were 99.4 and 99.5 percent, and the sensitivities were 98.0 percent and 99.4 percent [23,24]. In a single study not-included in the meta-analysis, the NPV was 98.9 percent and the sensitivity was 94.7 percent [25].
As discussed below, when strategies that rely on troponin values are combined with a clinical risk score, the accuracy of diagnosis is increased. (See 'Rationale' below.)
●ESC algorithms – The ESC 0/1-hour and 0/3-hour pathways are based on information from the initial troponin and the change between the first and second troponin values. In this paradigm, patients "rule out" if there is either a single hs-cTn below the limit of detection or if both the initial troponin is within normal limits and there is no increase in troponin between two assays. For example, one study that evaluated the ESC 0/1-hour algorithm excluded MI if the 0-hour troponin T value was <6 ng/L or if both the 0-hour value was <12 ng/L and the change between the 0-hour and 1-hour values was <3 ng/L [8]. Patients "ruled in" if either the 0-hour hs-cTnT was ≥52 ng/L or if the change in 0-hour and 1-hour values was ≥5 ng/L. Patients who did not clearly rule in or rule out were assigned to an intermediate observation designation.
Due to a lower prevalence of CAD in the United States (US) and a lower threshold to obtain troponin tests in the US, the ESC algorithms may have lower diagnostic accuracy in the US [26]. While large studies suggest a reasonable accuracy with the ESC 0/1-hour method (99 percent sensitivity for MI) [27], studies in specific subgroups suggest insufficient accuracy. In an analysis of the ESC 0/1-hour algorithm from eight sites in the US, patients with known CAD demonstrated a higher than accepted 30-day rate of death or MI, with an NPV of 96.6 percent (95% CI 92.8-98.8) [8]. In a subgroup of patients with known CAD who were managed with the ESC 0/1-hour algorithm, the NPV was 96.6 percent [28].
Among the ESC pathways, the 0/1-hour and 0/2-hour pathways have similar accuracy, while weak data suggest that the ESC 0/3-hour pathway may be more accurate for exclusion of MI than the ESC 0/1-hour pathway. In a study of patients who had data available to evaluate the 0/1-hour and 0/2-hour pathways, both methods had sensitivity of 98.2 percent and NPV of 99.8 percent [29]. In a trial in which patients were randomly assigned to management with a 0/1-hour pathway or to a 0/3-hour pathway, the rate of mortality or MI was nonsignificantly higher in patients assigned to the 0/1-hour pathway (5 versus 3.8 percent; hazard ratio 1.32, 95% CI 0.95-1.83) [30].
The rationale for using the HEART pathway rather than the ESC pathways is presented elsewhere in this topic. (See 'Rationale' below.)
●High-STEACS – In the HIGH-STEACS algorithm, patients are assigned to low-, intermediate-, and high-risk groups based on a single highly sensitive troponin value [31,32]. The sensitivity of this approach is 97.5 percent, and the NPV is 99.4 percent. In a trial that compared this protocol with usual care, the rates of death and MI were similar [33].
Rationale — Our preference for the two HEART Pathway methods is primarily based on weak data that suggest a higher, albeit small, increase in diagnostic accuracy with use of the HEART Pathways relative to other approaches. The HEART Score is well studied and has sufficient diagnostic accuracy across varying likelihoods of CAD (eg, early presentation, males and females, known history of CAD).
In one study that included 1462 patients with suspected NSTEMI who prospectively had all testing required to evaluate the modified HEART Score, single sample, and ESC 0/1-hour strategies, the modified HEART Score had the highest sensitivity (98.4 percent) and NPV (99.3 percent) for death or MI at 30 days [26]. Notably, sensitivity for the ESC 0/1-hour algorithm was 97.4 percent, and sensitivity for a single troponin near the limit of quantitation was 96.2 percent. In patients who presented less than three hours from the onset of symptoms, the sensitivity and NPV for the modified HEART Score were 100 percent sensitivity, 97.3 and 98.6 for a single troponin assay (regardless of ECG findings), and 91.3 and 97.8 percent for the ESC 0/1-hour algorithm (regardless of ECG findings).
Additional reasons that we prefer evaluation with the HEART Pathways include:
●Use of clinical criteria to identify high-risk patients – In patients with a HEART score ≥4 points, history of CAD, or ischemic ECG findings, further observation and testing are suggested regardless of troponin values based on the high risk of events in this group. (See 'Approach in high-risk patients' above.)
The ESC, single sample, and ACC Expert Consensus Pathway approaches do not explicitly triage patients based on clinical criteria alone. Among patients identified by clinical features alone using a modified HEART score, rates of death or MI varied between studies but were greater than 9 percent [15,17,18].
●Evaluation is more accurate with inclusion of clinical history and ECG findings – The explicit use of a clinical score increases the ability to accurately exclude MI by a small amount. In a study that primarily evaluated the ESC 0/1-hour algorithm, a single low troponin value (ie, near the limit of detection) had an NPV for 30-day major adverse cardiac events of 98.3 percent and sensitivity of 96.2 percent [26]. When this troponin value was sequentially combined with a HEART Score of 0 to 3 points and nonischemic ECG findings, diagnostic accuracy increased (NPV 99 percent, sensitivity 98.6 percent).
●Small changes in troponin may not be reliable – The ESC and single assay approaches use very small changes in troponin values that may be beyond the expected variability of such assays [34,35]. Repeat analysis of the same blood sample suggest that variation in the troponin assay results would change management in approximately 25 percent of patients [36].
INDETERMINATE TESTING OR ELEVATED RISK —
In patients in whom ACS cannot be reasonably excluded or confirmed, additional evaluation is typically required. In general, we prefer to evaluate such patients with an imaging study for obstructive CAD prior to discharge. However, highly selected patients may be evaluated in the outpatient setting if they are likely to adhere to plans for imaging or evaluation. The approach depends on the individual patient's scenario. Common scenarios include:
●Low risk with indeterminate troponin testing – For patients who are otherwise at low risk of ACS (eg, HEART Score 0 to 3 points) but whose troponin assays are indeterminate, we perform an additional troponin assay at three to six hours after the last troponin value. If this troponin value is positive or increases according to criteria in the algorithm in use, we manage the patient as suspected NSTEMI. (See "Non-ST-elevation acute coronary syndromes: Selecting a management strategy", section on 'Evidence of infarction (NSTEMI)'.)
In patients with persistently ambiguous results, imaging for obstructive CAD prior to discharge is a reasonable option and is discussed separately. (See "Noninvasive imaging for diagnosis in patients at low to intermediate risk for acute coronary syndrome", section on 'Patients whose symptoms have resolved'.)
●Known or elevated risk of obstructive CAD – In patients with known obstructive CAD or elevated clinical risk of obstructive CAD, reasonable options for management include imaging for obstructive CAD prior to discharge, imaging scheduled within 72 hours of discharge, and evaluation by a cardiologist within 72 hours of discharge. The specific approach depends on the severity of CAD and the acuity of factors that confer an elevated risk. In patients with remote CAD and few acute signs of CAD, it may be reasonable to proceed with an outpatient evaluation, while in patients in whom the risk of ACS is mostly due to acute findings (eg, new onset of typical symptoms, one risk factor for CAD, and nonspecific ECG changes), imaging prior to discharge may be optimal.
The choice of imaging study is discussed separately. (See "Noninvasive imaging for diagnosis in patients at low to intermediate risk for acute coronary syndrome", section on 'Patients whose symptoms have resolved'.)
This approach is based on our experience and limited studies that addressed the management of such patients:
●Among patients with a modified HEART Score between 4 and 6 points who were evaluated by a cardiologist within 72 hours, the rate of death or MI was 0.9 percent [15].
●In a randomized trial that included patients with suspected NSTEACS, the rate of death or MI at 30 days was high in patients with known CAD (17 percent) [15].
SPECIAL CIRCUMSTANCES
Other explanations for chest symptoms — In patients whose initial evaluation reveals another cause of chest symptoms (eg, pneumonia, bronchitis) and who are at low risk of ACS, further testing for ACS may not be necessary. However, in the presence of risk factors for ACS, it is important to keep ACS on the differential diagnosis even if an alternative diagnosis is more likely; the presence of another diagnosis does not exclude the presence of a type II MI. (See "Diagnosis of acute myocardial infarction" and "Diagnosis of acute myocardial infarction", section on 'Comparing type 1 and 2 myocardial infarction'.)
In patients being evaluated for chest pain, patients with a "clear-cut" alternative noncardiac diagnosis still have a 4 percent rate of ACS at 30 days [37]. Similarly, patients with a "clear-cut" alternative noncardiac diagnosis and a Thrombolysis in Myocardial Infarction (TIMI) risk score of 0 had a 2.9 percent rate of ACS at 30 days [38].
Atypical presentations — We suggest the use of HEART Pathways to minimize the risk of discharging patients with atypical presentations. The diagnosis of ACS is more likely to be missed in certain populations. In one study, patients diagnosed with ACS who were inappropriately discharged included females <55 years old, Black Americans, patients with dyspnea as the primary complaint, and patients with a normal ECG [39]. Older adults may also present with atypical histories [40,41].
Late presentation after symptom onset — In patients suspected of presenting late, downtrending troponin values should not provide false reassurance or mislead the clinician away from the diagnosis of NSTEMI [42]. Patients presenting days after experiencing an MI could present with troponin values below the upper reference limit. In such patients, we suggest a low threshold to pursue imaging for obstructive CAD, based on our experience.
Early presentation after symptom onset — In patients who present rapidly after the onset of symptoms (eg, within three hours), the history and ECG are most likely to confirm the diagnosis of NSTEMI. In this period, troponin levels may not be elevated. Thus, in such patients, we advise sequential evaluation of troponin values over at least two hours and longer if the presentation after the onset of symptoms is less than one hour.
Conditions with chronic troponin elevation — In patients with conditions likely to result in chronic troponin elevation (eg, left ventricular systolic dysfunction, chronic kidney disease), the evaluation for ACS should not rely on troponin assays alone. (See "Elevated cardiac troponin concentration in the absence of an acute coronary syndrome", section on 'Non-MI causes of an elevated troponin'.)
SOCIETY GUIDELINE LINKS —
Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Non-ST-elevation acute coronary syndromes (non-ST-elevation myocardial infarction)".)
SUMMARY AND RECOMMENDATIONS
●Goals of evaluation – The primary focus of the initial evaluation of patients with possible acute coronary syndrome (ACS) is to reasonably confirm or exclude the presence of ACS in an expeditious manner. ACS is reasonably excluded if there is a "very low risk" of ACS, which is generally considered to be a 30-day risk of death or ACS less than 1 or 2 percent, which correlates with a negative predictive value (NPV) and sensitivity of more than 98 or 99 percent. (See 'Goals of evaluation' above.)
●Initial tests and calculation of clinical risk – The initial tests for evaluation of non-ST-elevation ACS (NSTEACS) include an ECG, history and physical examination, troponin and other laboratory values (ie, electrolyte panel, kidney function, complete blood count), and chest radiography. (See 'Tests' above.)
In patients with suspected NSTEACS, we suggest calculating the modified HEART Score: (See 'Initial integrated risk assessment (HEART Score)' above.)
•History – If suspicion for ACS based on history is high, 2 points; if suspicion is moderate, 1 point; otherwise, 0 points.
•ECG – If the ECG shows ST-segment depression, 2 points; if nonspecific changes are present, 1 point; otherwise, 0 points.
•Age – If age is ≥65 years, 2 points; 45 to 64 years, 1 point; otherwise, 0 points.
•Risk factors – If the patient has ≥3 atherosclerotic risk factors, 2 points; if 1 or 2 risk factors, 1 point; otherwise, 0 points.
●Approach in high-risk patients – High-risk patients with suspected NTEACS include the following:
•Known history of CAD – In patients with a history of coronary artery disease (CAD; eg, prior myocardial infarction [MI], prior stenting or coronary artery bypass graft surgery, ≥70 percent obstruction on prior imaging) who have a history suspicious for NSTEACS but no ECG evidence of ischemia, additional evaluation for CAD is typically required. (See 'Known coronary artery disease' above and 'Indeterminate testing or elevated risk' above.)
•Ischemic ECG changes – Patients with ST depression >1 mm in two contiguous leads or T-wave inversion in a pattern consistent with ischemia should be observed in the hospital for management of suspected NSTEMI. In such patients, the approach to management may be further guided by the pattern of ECG changes (eg, resolution, worsening) and by troponin values. (See 'Ischemic ECG changes' above and "Non-ST-elevation acute coronary syndromes: Selecting a management strategy", section on 'Evidence of infarction (NSTEMI)'.)
•HEART Score ≥4 points – In patients in whom there is a high clinical suspicion for ACS based on symptoms and risk factors, it is most appropriate to offer testing with troponin values at time zero and at two hours for a high-sensitivity cardiac troponin (hs-cTn) assay and three hours for a conventional cTn assay. If troponin testing does not resolve the high clinical suspicion for ACS, additional troponin values (ie, at six hours) or prolonged observation with or without a stress or anatomic test for obstructive CAD are reasonable options. (See 'HEART Score ≥4 points' above and 'Indeterminate testing or elevated risk' above.)
●Approach in lower-risk patients – For most patients with suspected NSTEACS who present within 3 to 12 hours after symptom onset and who have no history of CAD and either a normal ECG or nonspecific ECG changes, we suggest evaluation with a protocol rather than with a less structured approach to evaluation (eg, serial troponins, clinical gestalt). (See 'Approaches in lower-risk patients' above.)
In patients with other presentations (eg, within one hour of symptom onset) and in certain scenarios (eg, persistent troponin elevation), particular protocols or alternative means of evaluation may be required. (See 'Special circumstances' above.)
It is reasonable to use the high-sensitivity HEART Pathway at centers with highly sensitive troponin assays or the modified HEART Pathway at centers with sensitive troponin assays (algorithm 1). The details on the use of these algorithms are discussed above. (See 'High-sensitivity troponin HEART Pathway' above and 'Modified HEART Pathway' above.)
Other approaches (eg, European Society of Cardiology [ESC] 0/1-hour pathway, single assay rule out) have limitations that limit their broad use. (See 'Other approaches' above.)
●Indeterminate testing or elevated risk – In patients in whom ACS cannot be reasonably excluded or confirmed, additional evaluation is typically required. In general, we prefer to evaluate such patients with an imaging study for obstructive CAD prior to discharge. However, highly selected patients may be evaluated in the outpatient setting if they are likely to adhere to plans for imaging or evaluation. The approach depends on the individual patient's scenario. (See 'Indeterminate testing or elevated risk' above.)
●Special circumstances – In patients with certain clinical features, the use of a standardized approach to evaluation may result in diagnostic errors. These groups include:
•Patients with a "clear-cut" cause for their presenting symptoms. (See 'Other explanations for chest symptoms' above.)
•Patients more likely to present with atypical symptoms. (See 'Atypical presentations' above.)
•Early and late presentation after the onset of symptoms. (See 'Late presentation after symptom onset' above and 'Early presentation after symptom onset' above.)
•Patients with chronic troponin elevation. (See 'Conditions with chronic troponin elevation' above.)
