Most urgent care providers loathe when a patient checks in with chest pain because, typically, they are presenting because they’re worried about a heart attack, and we’re worried we don’t have the tools to exclude this diagnosis. It’s no surprise that we’re met with consternation when we suggest they may have come to the wrong place for care. But is unavailability of troponin testing a worthy scapegoat? And is the practice of ED referral for nearly every patient with chest pain appropriate?

I propose we reevaluate the typical approach to chest pain in UC. 

Chest Pain Is Common, but Myocardial Infarction Is Rare in Urgent Care

Chest pain is concerning to patients predominantly due to the possibility of myocardial infarction (MI), which represents between 1% and 3% of ambulatory visits for acute complaints.1 While this is a small proportion of overall visits, it means we will see patients like this nearly every shift. 

The vast majority of patients seeking care for acute chest pain aren’t having a heart attack. In fact, only about 10%-12% of patients presenting to an ED with concerns for acute coronary syndrome (ACS) will go on to have a major adverse cardiac event  (MACE), within the subsequent 30 days.2,3 Rates of immediate ACS in ED populations are even lower (5%-10%).4

Frequency of short-term MACE and immediate ACS have not been specifically studied in U.S. urgent care populations, but are likely significantly less than those observed in the ED. The best estimate from the recent literature which can be extrapolated to UC comes from a European study of acute primary care visits, where the investigators found the 6-week risk of MACE to be <5%.1

Most Studies of Chest Pain Measure the Wrong Outcomes

Immediate risk of ACS and what to do with the patient in front of us reporting chest symptoms in that moment is our primary concern in UC. Unfortunately, most studies reporting outcomes of patients with acute chest pain fail to be directly relevant for the UC clinician not only because they’re ED-based, but also because they report MACE over the subsequent weeks as their primary endpoint. 

The concept of MACE was developed in the late 1990s by cardiologists as a composite endpoint for measuring outcomes after coronary interventions (PCI).5 Patients are classified as having a MACE if they die, have an MI, or have a repeat PCI during some specified period of time, usually 4-6 weeks. While convenient for statistical analysis, these composite endpoints are difficult to interpret, as death and “needing to have a procedure” are far from equivalent outcomes. However, research using MACE counts these events equally. 

A second problem is that the timeline for cardiac events measured in many studies is not relevant to our clinical predicament.6 We seek to know the near-term safety of the patient, ie, will they drop dead before they can make it to the ED if the chest pain comes back? If we knew they could make it to outpatient follow-up, we’d feel much more comfortable foregoing an immediate ED referral.

Unfortunately, a trend among many studies examining the various ACS clinical decision rules (CDR) is that they look at MACE over a longer time period (usually around 1 month) than is relevant to UC providers.6 This is problematic because immediate risk for sudden death or serious MI in UC patients has not been specifically studied. In other words, it’s certainly lower, but we really can’t say how much lower without UC-specific data.

Clinicians Do Not Tolerate Uncertainty when Considering ACS

A recent study by Samuels, et al found that among 126 emergency providers of varying roles, half were uncomfortable with missing an acute myocardial infarction (MI) even 0.1% of the time.7 Even though the American College of Emergency Physicians (ACEP) has stated that an ACS miss rate of 1% to 2% is acceptable—perhaps even unavoidable—acute care providers continue to approach patients with chest pain with an overabundance of caution. 

The rationale for this is related to fear of litigation, which is a valid concern as “failure to diagnose” MI remains a leading cause of U.S. malpractice claims.8 But if we could say with confidence that there’s a less than 2% chance of MI, we’d be well protected by the ACEP policy and the current stream of excessive ED referrals, testing, and admissions could be significantly mitigated. Over the past decade, several CDRs have been developed to address this very conundrum, with the HEART score being the most prominent and well validated. But there’s a catch.

Most ACS Prediction Tools Don’t Work in Urgent Care 

Outpatient risk stratification tools for patients presenting with chest pain have been sought after for several decades. This is because clinician gestalt has been proven unreliable consistently in ruling out cardiac etiologies of chest symptoms. The aim of these CDRs was to take provider subjectivity out of the calculation; however, none have really met the needs of the UC clinician. 

A number of these rules (eg, Marburg, Gencer, INTERCHEST) were developed for use in primary care. While it is helpful that these rules do not require troponin testing (or even an EKG), they were designed to predict whether patients’ symptoms are due to coronary artery disease (CAD), not ACS. These tools not only fail to address the question we’re trying to answer in UC, they also don’t do an adequate job of even answering the question they were developed for (ie, CAD or not), with sensitivities ranging from 81% to 88%.1

The Bruins Slot rule is a unique tool developed with the aim ruling out ACS (rather than CAD) in an ambulatory setting without an EKG or troponin. While promising in concept, its real-world performance falls short of holy grail status with a sensitivity of ~90%.1 

For ED patients, on the other hand, the recent development of the HEART and EDACS scores has proven to be highly useful in identifying a large proportion of patients presenting with concerns for ACS who can safely be discharged without further immediate work-up. These tools, especially the HEART score, have been widely adopted by emergency clinicians who now can discharge many more patients with chest pain and still sleep well at night.9 The catch: these tools all require serum troponin testing, which is only available in <10% of U.S. urgent care centers. 

A HEAR(-T) Score for the Rest of Us

The HEART score, first developed in 2008,10 is a clever acronym which combines 1) history, 2) EKG findings, 3) age, 4) CAD risk factors, and 5) troponin values to categorize patients as low, moderate, or high risk for ACS. Since being introduced, the HEART score has been validated by multiple investigators and has been found to be a reliable means of risk stratifying patients with chest pain for risk of MACE over the subsequent weeks, with a sensitivity >98% for low HEART score patients.11 

However, the necessity of troponin testing for the calculation of a HEART score has left UC providers feeling somewhat appropriately resigned to continue the status quo practice of near-automatic ED referrals for all but the lowest risk patients (read: anxious adolescents). This has resulted in an abundance of low-risk ED referrals with an accompanying line in the chart: “Cannot r/o ACS without troponin.” But do we actually need a troponin to exclude ACS in low-risk patients with chest pain? 

While the HEART score may be the most well-known clinical decision tool for chest pain presentations, its lesser-known cousin the “HEAR” or “HEAR(-T)” score has recently been externally validated with promising results. It seems the dogma of mandatory troponin testing when considering ACS may not be as ironclad as we’ve thought over recent decades—especially for the very low-risk patients. 

In 2020, Smith, et al first described the use of a HEART score without troponin testing applied retrospectively to over 4,000 ED patients from the original HEART score study population.2 They found that a HEAR score of 0 or 1 occurred in 9% of patients and was 97.8% sensitive for ruling out 30-day MACE in this population. As ACEP has codified the 2% acceptable miss rate for ACS, this sensitivity almost exactly meets the minimum necessary for an acceptable “test” to be clinically useful in this situation. (Interestingly, the addition of a single troponin in this study did not improve the sensitivity of the rule either.)

More recently, O’Reilly and colleagues published the results of an external validation of the HEAR score.12 They performed a secondary analysis of data collected in a prospective cohort study of 820 patients presenting in an urban Canadian ED with symptoms concerning for ACS. Improving on the clinical utility of the original HEAR study, O’Reilly et al included patients with known CAD (who were excluded from the initial study) and used both 30-day MACE and immediate risk of MI diagnosed within 24 hours of ED presentation as co-primary endpoints. Importantly, patients with ischemic changes or new arrhythmia on EKG, advanced renal failure, MI within the prior month, and those under 25 years of age were excluded. 

They found that nearly 25% of patients had a HEAR score of 0 or 1. Confirming that low- risk patients are indeed low risk for bad near-term outcomes, only one patient in the low-risk group (score of 0 or 1) had an MI or 30-day MACE event. This yielded a sensitivity of HEAR <2 for 30-day risk of MACE or immediate MI of 98.3- 99.2%. Better yet, for patients with a HEAR score of 0, the sensitivity was 100%.

This study understandably did not receive nearly the fanfare as the original HEART score studies among the emergency medicine community because troponin testing for chest pain patients in the ED is literally automatic. However, the authors fail to make mention of the tremendous potential utility of this decision rule for UC clinicians who don’t have instant troponin testing available with a click of the mouse. 

Given that UC centers tend to see younger, healthier, lower acuity patients with chest pain compared to ED the population, it’s likely that an even greater proportion of UC patients will actually fall into this low-risk (ie, score 0 or 1) group. This means that by applying the HEAR rule there is now an evidence base for discharging low-risk patients directly from UC. Coupled with the support of ACEP’s clinical policy on acceptable ACS miss rates, UC providers should feel confident that this is a reasonable practice. Plus, this approach will be preferred by nearly every low-risk patient you see.

Cautions in Applying the HEAR Score

If this is your first introduction to the HEAR score, hopefully you’re feeling more enthusiastic than skeptical at this point. For the enthusiasts, however, it is important to remember the limitations of CDRs in clinical practice.

First, CDRs, including the HEAR score, are developed to exclude conditions, rather than to make diagnoses.13 Patients with HEAR scores of 0 or 1 can be safely presumed to be low enough risk for discharge from UC without immediate ED referral, but patients with scores >1 do not necessarily warrant immediate 911 activation. It is just not appropriate to use the HEAR score to justify your disposition decision in such patients. In other words, a “negative” HEAR score is meaningful but, a “positive” result is not. In fact, the specificity of a score >1 for one of the adverse cardiac outcomes was an unimpressive 19%-26% in the O’Reilly validation study.12 

Secondly, a CDR can only be applied validly to the same type of patients as those who were included in the studies from which it was derived. For example, patients under 25 years and with end-stage renal disease were excluded in the HEAR validation study. Therefore, the rule can’t be relied upon in these patients unless a subsequent study produces similar results and does not exclude these patients. 

A New Approach to When Considering ACS in UC

Hopefully at this point, you’re reconsidering the “business as usual approach” to UC patients with chest pain. Although most patients with chest pain who present to UC are exceptionally low risk for ACS (and even more so for sudden cardiac death), providers are extremely intolerant of missing an MI. A recent ACEP policy statement, however, provides top cover for an approach to evaluation for ACS that results in a miss rate <2%.14 

While the original HEART score is inaccessible to most UC clinicians due to lack of troponin testing, the ability to obtain an EKG is nearly universal. So ,when patients present to your UC center with chest pain or symptoms that create concerns for ACS, they can be approached initially in the standard fashion: rapid rooming, vitals, and EKG. If the patient has a STEMI or other clear signs of ischemia, 911 activation is appropriate. However, this is rarely the case. For the vast majority of patients, the EKG will be reassuring and you’ll be able to take some time to look up and apply the HEAR score.

With a reassuring history and EKG, a large proportion of patients can safely be ruled out for immediate and 30-day MACE (provided the HEAR is score <2).

For the rest of the patients, we can continue to use our clinical gestalt, appreciating its shortcomings, as well as shared decision-making regarding the necessity of immediate vs PRN ED referral and 911 activation.

Applying this strategy in chest pain management rather than quickly dismissing patients due to lack of troponin testing will be appreciated by your patients, who certainly want to avoid the ED if possible. Most importantly, it will achieve this in an evidence-based fashion—avoiding bad outcomes not only for our patients, but for ourselves as well.

REFERENCES

  1. Kleton M, Manten A, Smits I, et al. Performance of risk scores for coronary artery disease: a retrospective cohort study of patients with chest pain in urgent primary care. BMJ Open. 2021;11(12):e045387.
  2. Smith LM, Ashburn NP, Snavely AC, et al. Identification of very low-risk acute chest pain patients without troponin testing. Emerg Med J. 2020;37(11):690-695.
  3. Weinstock MB, Weingart S, Orth F, et al. Risk for clinically relevant adverse cardiac events in patients with chest pain at hospital admission. JAMA Intern Med. 2015;175(7):1207–1212.
  4. Fanaroff AC, Rymer JA, Goldstein SA, et al. Does this patient with chest pain have acute coronary syndrome? The rational clinical examination systematic review. JAMA. 2015;314(18):1955-1965.
  5. Serruys PW, van Der Giessen W, Garcia E, et al. Clinical and angiographic results with the multi-link stent implanted under intravascular ultrasound guidance (West-2 Study). J Invasive Cardiol. 1998;10(Suppl B):20B-27B.
  6. Weinstock MB, Finnerty NM, Pallaci M. Time to move on: redefining chest pain outcomesJ Am Heart Assoc. 2019;8(12):e012542.
  7. Samuels R, Cocchiarale F, Dutta S, et al. What is the acceptable miss rate for a major adverse cardiac event (MACE)? A follow-up survey after release of the American College of Emergency Physicians (ACEP) clinical policy on acute coronary syndromes. J Urgent Care Med. 2022;16(8):33-37.
  8. Brown TW, McCarthy ML, Kelen GD, Levy F. An epidemiologic study of closed emergency department malpractice claims in a national database of physician malpractice insurers. Acad Emerg Med. 2010;17(5):553-560.
  9. Mahler SA, Burke GL, Duncan PW, et al. HEART pathway accelerated diagnostic protocol implementation: prospective pre-post interrupted time series design and methods. JMIR Res Prot. 2016;5:e10.
  10. Six AJ, Cullen L, Backus BE, et al. The HEART score for the assessment of patients with chest pain in the emergency department: a multinational validation study. Crit Pathw Cardiol. 2013;12(3):121-126.
  11. Backus BE, Six AJ, Kelder JC, et al. A prospective validation of the HEART score for chest pain patients at the emergency department. Int J Cardiol. 2013;168(3):2153–2158.
  12. O’Reilly CM, Andruchow JE, McRae AD. External validation of a low HEAR score to identify emergency department chest pain patients at very low risk of major adverse cardiac events without troponin testing. CJEM. 2022;24(1):68–74.
  13. Adams ST, Leveson SH. Clinical prediction rules. BMJ. 2012;344:d8312.
  14. American College of Emergency Physicians Clinical Policies Subcommittee (Writing Committee) on Suspected Non–ST-Elevation Acute Coronary Syndromes: Tomaszewski CA, Nestler D, Shah KH, et al. 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.

Joshua Russell, MD, MSc, FCUCM, FACEP is Editor-in-Chief of JUCM, The Journal of Urgent Care Medicine; attending staff physician, NorthShore University Health System (Teaching Affiliate of the University of Chicago); Associate Editor, Urgent Care Reviews and Perspectives Podcast, Hippo Education; and staff physician, Legacy/GoHealth Urgent Care. Michael B. Weinstock, MD is Senior Editor, Clinical Content for JUCM; Director of Research and Medical Education, Adena Health Systems; Professor of Emergency Medicine Adjunct, The Ohio State University Department of Emergency Medicine; Executive Editor, Urgent Care Reviews and Perspectives (UC RAP); and Medical Director, Ohio Dominican University Physician Assistant studies program.

Read More on Chest Pain

No Troponin, No Problem: Reimagining Chest Pain Assessment in Urgent Care
Joshua Russell, MD

Joshua Russell, MD, MSc, FAAEM, FACEP

Quality and Provider Education, Legacy - GoHealth Urgent Care, is affiliated with the University of Chicago Medical Center in Vancouver, WA, and is Editor-in-Chief of JUCM.

Michael B. Weinstock, MD

Associate Program Director, Adena Emergency Medicine Residency; Director of Research and CME, Adena Health System; Professor of Emergency Medicine, Adjunct, Department of Emergency Medicine, Wexner Medical Center at The Ohio State University; Senior Clinical Editor, The Journal of Urgent Care Medicine (JUCM)
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