GPAC: Guidelines and Protocols Advisory Committee

Chest Pain - Evaluation of Acute Coronary Syndromes

Effective Date: November 1, 2003

Summary | Flow Sheet | Patient Guide | Full Guideline in PDF

Recommendations and Topics

Scope

1. Selection of patients who may have ACS

2. Initial evaluation in emergency department

3. Management of high-risk patients

4. Management of patients without high-risk features

Table 1

Table 2: Risk Stratification

Figure 1: Evaluation of Acute Chest Pain

Rationale

References

Sponsors

Scope

Objective: To improve the identification of patients with acute coronary syndromes (ACS): acute myocardial infarction and unstable angina. To reduce the number of patients with ACS sent home in error after initial evaluation. This guideline does not address chronic stable angina.

Target Population: Adults presenting with chest pain in physicians' offices, walk-in clinics and emergency departments.

RECOMMENDATION 1: Selection of patients who may have ACS

Patients presenting with prolonged (more than 10 minutes) acute chest pain suggestive of ACS (see Table 1) should be evaluated by a history and physical examination. If a patient presents in a physician's office or walk-in clinic and no alternative cause can be found, the patient should be sent to the Emergency Department for further evaluation and observation. A patient who is suspected of having an acute coronary syndrome should not be sent to a laboratory for an ECG or measurement of cardiac markers.

RECOMMENDATION 2: Initial evaluation in emergency department

Patients with chest pain suggestive of acute coronary syndromes (ACS) should be evaluated with a history, physical examination, an electrocardiogram (ECG) and cardiac markers*, preferably troponin.

*The term cardiac markers refers to proteins such as troponin I and T, creatinine kinase MB (CK-MB) and myoglobin, which are released into the blood after heart muscle necrosis. Emergency rooms should have troponin tests available.

RECOMMENDATION 3: Management of high-risk patients

Patients with ST segment elevation and/or definite elevation of cardiac markers should be treated immediately with the intent of opening the infarct-related artery and maintaining perfusion. Patients with a compatible history and a clearly abnormal ECG (without ST elevation), moderately elevated cardiac markers or hemodynamic compromise should be treated for acute myocardial ischemia.

RECOMMENDATION 4: Management of patients without high-risk features

Patients with a compatible history, but without high-risk features should have an ECG and cardiac markers, preferably troponin, performed at 6 or more hours after onset of pain.

Patients with elevated cardiac markers or abnormal ECG at 6 hours should be admitted and treated for acute myocardial ischemia.

Patients without elevated cardiac markers at 6 or more hours and normal ECG should be considered low or intermediate risk according to the accompanying table.

Intermediate risk patients where clinical suspicion remains high but tests at 6 hours are negative should have a stress test (with or without a radionuclide scan) prior to discharge.

Low-risk patients without an obvious alternative explanation for the chest pain should have urgent out-patient physician follow-up, advice to return if the pain recurs and arrangements for an out-patient stress test (with or without radionuclide scan).

Table 1:

Table 2: Risk Stratification

Figure 1: Evaluation of Acute Chest Pain

Rationale

The diagnosis of acute coronary syndromes (ACS) among patients with chest pain is easily missed because no single objective test reliably identifies ACS in these patients.¹ Inappropriate discharge can lead to preventable acute myocardial infarction (AMI) or sudden death.² A recent Canada-US study³ showed that 57-99% of patients presenting to an emergency department with chest pain were admitted for further investigation. In the participating Canadian hospitals only 13-51% of admitted patients ultimately proved to have an acute coronary syndrome. Some US centres have established chest pain evaluation units (CPEUs) to limit unnecessary coronary care unit (CCU) admissions. These CPEUs apply 9-12 hour step-wise AMI rule out protocols using observation, serial ECGs and cardiac markers, provocative tests and cardiac imaging. The CPEUs have reported reduced costs and improvements in the identification of ACS compared with facilities that admit all patients to the CCU. Chest pain units are not established in British Columbia partly because their true cost-effectiveness is unknown.

Clinical variables associated with ACS include gender, age, family history, previous angina or AMI, pain characteristics, syncope, response to nitro-glycerine, diaphoresis, nausea and vomiting, blood pressure, rales, jugular venous distensions, heart sounds, descriptive gestures and arrhythmias. Many of the above are strong predictors of ACS but their clinical utility in individual patients is uncertain.⁴ Women, in particular, often do not complain of typical chest pain and present with atypical symptoms.

ECG abnormalities are strong positive predictors but as many as 82% of patients with ACS-related chest pain have normal or near normal ECGs.⁵

Cardiac markers including CK-MB, myoglobin and troponins are released during AMI. The sensitivity of CK-MB assays and troponins improves with serial testing but never reaches levels high enough at the initial assessment to rely on markers alone to rule out AMI or unstable angina.⁶

Stress tests may be dangerous in high risk patients, require skilled interpretation and have limited availability outside major centres.

In a recent ongoing evaluation in two Vancouver hospitals, 4.5% of patients with an AMI and 6.8% of patients with unstable angina were discharged with a non-ACS diagnosis.⁷Most clinicians consider these rates too high. The need for a clinical decision tool is urgent and there is great potential for improvements in detecting ACS.

Diagnostic uncertainty leaves physicians with a difficult decision: to discharge and risk missing a potentially lethal diagnosis, or to admit for an expensive investigation. The most difficult cases of ACS to identify are those with chest pain but negative ECGs and cardiac enzymes. The American Heart Association (AHA) has recently published a guideline for the management of patients with unstable angina and non-ST elevation myocardial infarction (NSTEMI).⁸ The algorithm from the AHA guideline has been adapted (see Figure 1) to help BC physicians manage patients who present with chest pain in the ambulatory setting. A table of risk features is also provided (Table 1) to aid in diagnosis. This table is adapted from work by Fitchett et al.⁹ who modified the AHA/ACC guideline for the Canadian setting. The objective of this guideline is to reduce the rate of missed cases of myocardial infarction and unstable angina sent home in error.

References

1. Dagnone E, Collier C, Pickett W, Ali N, Miller M, Tod D and R Morton. Chest pain with nondiagnostic electrocardiogram in the emergency department: a randomized controlled trial of two cardiac marker regimens. CMAJ 2000;162(11):1561-6.
2. Lee TH, Rouan GW, Weisberg MC, Brand DA, Acampora D, Stasiulewicz C, et al. Clinical characteristics and natural history of patients with acute myocardial infarction sent home from the emergency room. Am J Cardiol 1987;60(4):219-24.
3. Gibler WB, Hoekstra JW, Weaver WD, Krucoff MW, Hallstrom AP, Jackson RE, et al. A randomized trial of the effects of early cardiac marker availability on reperfusion therapy in patients with acute myocardial infarction: The serial markers in acute myocardial infarction and rapid treatment trial. J Am Coll Cardiol 2000;36(5):1500-6.
4. Panju AA, Hemmelgarn BR,Guyatt GH, Simel DL. Is this patient having a myocardial infarction? JAMA 1998; 280(14):1256-1263.
5. Fesmire FM, Percy RF, Bardoner JB, Wharton DR, Calhoun FB. Usefulness of automated serial 12-lead ECG monitoring during the initial emergency department evaluation of patients with chest pain. Ann Emerg Med 1998;31(1):3-11.
6. Antman EM, Tanasijevic MJ, Thompson B, Schactman M, McCabe AH, Cannon CP, et al. Cardiac-specific troponin I levels to predict the risk of mortality in patients with acute coronary syndromes. NEJM 1996;335(18):1342-9.
7. Christenson J. Emergency Medicine , St. Paul's Hospital 2001. Unpublished data.
8. Braunwald E, Antman EM, Beasley JW, Califf RM, Cheitlin MD, Hochman JS, et al. ACC/AHA guidelines for the management of patients with unstable angina and non-ST segment elevation myocardial infarction: Executive summary and recommendations. Circulation 2000;102(10):1193-209.
9. Fitchett D, Goodman S, Langer A. New advances in the management of acute coronary syndromes: 1. Matching treatment to risk. CMAJ 2001;164(9):1309-16.

Sponsors

This guideline was developed by the Guidelines and Protocols Advisory Committee, approved by the British Columbia Medical Association and adopted by the Medical Services Commission.

Funding for this guideline was provided in full or part through the Primary Health Care Transition Fund.

Revised Date: April 1, 2007

This guideline is based on scientific evidence current as of the effective date.

Disclaimer

The Clinical Practice Guidelines (the "Guidelines") have been developed by the Guidelines and Protocols Advisory Committee on behalf of the Medical Services Commission. The Guidelines are intended to give an understanding of a clinical problem, and outline one or more preferred approaches to the investigation and management of the problem. The Guidelines are not intended as a substitute for the advice or professional judgment of a health care professional, nor are they intended to be the only approach to the management of clinical problems.

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