Consistently, 6–8 million patients visit to the emergency department (ED) for chest pain annually, with about 15% ultimately diagnosed with acute coronary syndrome (ACS) . Despite improved biomarker sensitivity, the risk of missed diagnosis of ACS remains high, with estimates remaining approximately 2% at 7 days . Furthermore, there is significant variation among hospitals and clinicians, with one recent study showing miss rates between 0% and 26% . The risk-adjusted mortality of discharged patients is nearly twice of those patients hospitalized with ACS .
Missed diagnosis of ACS tops the list of highest dollar awards in malpractice cases every year in the United States, accounting for nearly 30% of all dollars paid out. Whereas missed fracture and infection cases are more common malpractice lawsuits overall, missed ACS awards are so high because the cases often end in death or severe disability of relatively young and seemingly “healthy” patients . Given these parameters, emergency physicians have a low risk tolerance for missed cases. In a recent international survey of emergency medicine physicians, over 85% of physicians believe that the acceptable miss rate is <1% .
Thus, for the emergency physician, the question is who are the low risk patients who do not need any further testing? Current guidelines by the American Heart Association (AHA) and American College of Cardiology (ACC) are unclear; the recommendation is that “stable patients with no objective evidence of ischemia are considered low risk and can be admitted to an observation unit for further evaluation by an accelerated diagnostic protocol” . The guidelines further define “low risk” as a probability of myocardial infarction (MI) of <6%. For these patients, “a negative evaluation is followed by a confirmatory study to exclude inducible ischemia” . The confirmatory studies recommended by the guidelines include exercise treadmill testing and cardiac imaging. Effectively, these guidelines require that patients receive both an AMI “rule out” and an assessment for underlying coronary disease or inducible ischemia.
Low risk cannot be defined by physician history or physical examination; these tools have not been proven to be a powerful enough predictive tool to obviate the need for at least some diagnostic testing . Combinations of elements of the chest pain history with other initially available information, such as a history of coronary artery disease (CAD), have identified certain groups that may be safe for discharge without further evaluation, but further study is needed before such a recommendation can be considered reasonable. Those patients whose physicians felt had a clear-cut noncardiac diagnosis for their chest pain still have up to a 4% risk of adverse cardiovascular event within 30 days . In order to objectively evaluate the risk, risk stratification tools help physicians define the pretest probability of patients. The most commonly used scores include the Thrombolysis in Myocardial Infarction (TIMI) risk score. The TIMI risk score was derived from the original score developed for unstable angina and non-ST elevation myocardial infarction (NSTEMI). Its use for risk stratification in the ED population has been validated in several studies. However, a TIMI score of 0 still presents almost a 2% risk of 30-day adverse cardiovascular events, limiting its use as a tool for the rapid discharge of patients . Physician judgment of a clear-cut alternative diagnosis in those with low TIMI risk scores still had a significant 2.9% risk of 30-day adverse cardiovascular events . The only patient group that does not need further risk stratification are patients younger than 40 years old with chest pain: in these young adult patients without a known cardiac history, either no classic cardiac risk factors or a normal electrocardiogram (ECG), and initially normal cardiac marker studies, the risk of ACS was also extremely low (0.14%) and there were no adverse events at 30-day follow-up .
The HEART score was developed more recently and gives some flexibility with 0, 1, or 2 points for each category of history, ECG findings, age, risk factors, and troponin values. In one prospective validation study by the creators of the score, 2440 patients were enrolled. Those with a low HEART score (values 0–3) represented 36.4% of the study population. Six-week major adverse cardiovascular event (MACE) occurred in 15 out of 870 (1.7%) patients . Although these risk scores help stratify patients, they do not identify a cohort of patients at low enough risk for no further testing.
The incremental benefit of cardiovascular testing and imaging depends on the pretest probability of the patient being evaluated. In a low pretest probability patient cohort, a diagnostic test with a high likelihood ratio negative is necessary to meet that acceptable miss rate of <1%. Exercise stress testing had negative likelihood ratios of 0.28 in the low risk patient population . A recent meta-analysis showed a pooled negative likelihood ratio for coronary CT angiography (CTA) of 0.11 at a per-segment level. Assuming a low pretest probability, the posttest probability for any of these imaging studies would be <2%.
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Table 1
Comparison of Risk Stratification Scores
TIMI Risk Score HEART Score Age ≥65 years Yes = 1 History Highly suspicious 2 No = 0 Moderately suspicious 1 ≥3 risk factors for CAD Yes = 1 Slightly or nonsuspicious 0 No = 0 ECG Significant ST depression 2 ST deviation ≥0.5 mm Yes = 1 Nonspecific repolarization disturbance 1 No = 0 Normal 0 Known CAD (stenosis ≥50%) Yes = 1 Age ≥65 years 2 No = 0 >45–<65 years 1 ↑ Cardiac markers Yes = 1 ≤45 years 0 No = 0 Risk factors ≥3 risk factors, or history of atherosclerotic disease 2 ASA use in past 7 days Yes = 1 1 or 2 risk factors 1 No = 0 No risk factors known 0 Recent (≤24 h) severe angina Yes = 1 Troponin ≥3 × normal limit 2 No = 0 >1–< 3 × normal limit 1 ≤Normal limit 0
ASA, aspirin; CAD, coronary artery disease; ECG, electrocardiogram; TIMI, Thrombolysis in Myocardial Infarction.
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References
1. Bhuiya F.A., Pitts S.R., McCaig L.F.: Emergency department visits for chest pain and abdominal pain: United States, 1999–2008. NCHS Data Brief 2010; 43: pp. 1-8.
2. Abstract: missed diagnoses of acute myocardial infarction in the emergency department: an exploration using HCUP data. Available at: https://smdm.confex.com/smdm/2010on/webprogram/Paper5991.html Accessed June 19, 2016
3. Pope J.H., Aufderheide T.P., Ruthazer R., et. al.: Missed diagnoses of acute cardiac ischemia in the emergency department. N Engl J Med 2000; 342: pp. 1163-1170.
4. Schull M.J., Vermeulen M.J., Stukel T.A.: The risk of missed diagnosis of acute myocardial infarction associated with emergency department volume. Ann Emerg Med 2006; 48: pp. 647-655.
5. Katz D.A., Williams G.C., Brown R.L., et. al.: Emergency physicians’ fear of malpractice in evaluating patients with possible acute cardiac ischemia. Ann Emerg Med 2005; 46: pp. 525-533.
6. Kachalia A., Gandhi T.K., Puopolo A.L., et. al.: Missed and delayed diagnoses in the emergency department: a study of closed malpractice claims from 4 liability insurers. Ann Emerg Med 2007; 49: pp. 196-205.
7. Than M., Herbert M., Flaws D., et. al.: What is an acceptable risk of major adverse cardiac event in chest pain patients soon after discharge from the emergency department?: a clinical survey. Int J Cardiol 2013; 166: pp. 752-754.
8. Amsterdam E.A., Kirk J.D., Bluemke D.A., et. al.: Testing of low-risk patients presenting to the emergency department with chest pain. A scientific statement from the American Heart Association. Circulation 2010; 122: pp. 1756-1776.
9. Swap C.J., Nagurney J.T.: Value and limitations of chest pain history in the evaluation of patients with suspected acute coronary syndromes. JAMA 2005; 294: pp. 2623-2629.
10. Hollander J.E., Robey J.L., Chase M.R., et. al.: Relationship between a clear-cut alternative noncardiac diagnosis and 30-day outcome in emergency department patients with chest pain. Acad Emerg Med 2007; 14: pp. 210-215.
11. Chase M., Robey J.L., Zogby K.E., et. al.: Prospective validation of the Thrombolysis in Myocardial Infarction risk score in the emergency department chest pain population. Ann Emerg Med 2006; 48: pp. 252-259.
12. Hess E.P., Perry J.J., Calder L.A., et. al.: Prospective validation of a modified thrombolysis in myocardial infarction risk score in emergency department patients with chest pain and possible acute coronary syndrome. Acad Emerg Med 2010; 17: pp. 368-375.
13. Campbell C.F., Chang A.M., Sease K.L., et. al.: Combining Thrombolysis in Myocardial Infarction risk score and clear-cut alternative diagnosis for chest pain risk stratification. Am J Emerg Med 2009; 27: pp. 37-42.
14. Marsan R.J., Shaver K.J., Sease K.L., et. al.: Evaluation of a clinical decision rule for young adult patients with chest pain. Acad Emerg Med 2005; 12: pp. 26-31.
15. Backus B.E., Six A.J., Kelder J.C., et. al.: A prospective validation of the HEART score for chest pain patients at the emergency department. Int J Cardiol 2013; 168: pp. 2153-2158.
16. Banerjee A., Newman D.R., Van den Bruel A., et. al.: Diagnostic accuracy of exercise stress testing for coronary artery disease: a systematic review and meta-analysis of prospective studies. Int J Clin Pract 2012; 66: pp. 477-492.
17. Than M., Cullen L., Aldous S., et. al.: 2-Hour accelerated diagnostic protocol to assess patients with chest pain symptoms using contemporary troponins as the only biomarker: the ADAPT trial. J Am Coll Cardiol 2012; 59: pp. 2091-2098.
18. Mahler S.A., Riley R.F., Hiestand B.C., et. al.: The HEART pathway randomized trial identifying emergency department patients with acute chest pain for early discharge. Circ Cardiovasc Qual Outcomes 2015; 8: pp. 195-203.
19. Mokhtari A., Dryver E., Söderholm M., et. al.: Diagnostic values of chest pain history, ECG, troponin and clinical gestalt in patients with chest pain and potential acute coronary syndrome assessed in the emergency department. Springerplus 2015; 4: pp. 219.
20. Chang A.M., Pitts J., Shofer F.S., et. al.: Validation of a clinical decision rule for ED patients with potential acute coronary syndromes. Acad Emerg Med 2011; 19: pp. S18.
21. Story M., Reynolds B., Bowser M., et. al.: Barriers to outpatient stress testing follow-up for low-risk chest pain patients presenting to an ED chest pain unit. Am J Emerg Med 2016; 34: pp. 790-793.
22. Milano P., Carden D.L., Jackman K.M., et. al.: Compliance with outpatient stress testing in low-risk patients presenting to the emergency department with chest pain. Crit Pathw Cardiol 2011; 10: pp. 35-40.
23. Richards D., Meshkat N., Chu J., et. al.: Emergency department patient compliance with follow-up for outpatient exercise stress testing: a randomized controlled trial. CJEM 2007; 9: pp. 435-440.
24. Hess E.P., Hollander J.E., Schaffer J.T., et. al.: Involving patients with low-risk chest pain in discharge decisions: a multicenter trial. (2016), SAEM Annual Meeting Abstracts. Acad Emerg Med 2016; 23: pp. S7-S276.